Opalescence is a pretty interesting card. I might not say ban worthy, but interesting. My Hanna, Ship's Navigator deck revolves around Opalescence, so I'd hope it's not banworthy.

Opalescence with Parallax Wave
Opalescence/Parallax Wave with:
Venser, Shaper Savant to bounce all spells and all permanents always.
Glimmerpoint Stag to exile all permanents always.
Draining Whelk to counter all spells.
Soul Warden for infinite life.
Sea Gate Oracle for infinite filter/draw.
Cunning Sparkmage for infinite damage.
Oblivion Ring to permanently exile all nonland permanents.

Opalescence with Enchanted Evening to destroy all lands perpetually. If I control a signet, or artifact source of mana, I can also use this (with Wave) to always have infinite mana.

This sounds more like something fun (and convoluted) to set up than something game-breaking.

If you were playing green you could basically obliterate an opponent by playing that card that destroys all of a target player's enchantements (forget the name at the moment).

Opalescence decks were annoying in the day because people packed Frantic Search, Replenish x 4, Parallax Tide/Wave, etc. etc.
These days, I expect that while some people might not enjoy being locked down or so on, this might be on the "bizarre" end and not the "Rofellos/Umbral Mantle/Channel/Emrakul turn early" end of things.

Then again, who knows, the RC might right now be pondering Opalescence's danger to the EDH equilibrium.

I'm confused. What does this have to do with Staff of Domination?

Well, if Staff of Domination got the boot for being a "combo instigator" insofar as that Staff is not necessarily broken all by its lonesome, but unbanned presents an incentive, and relatively easy method of achieving, for infinite combos, then technically doesn't Opalescence also fit that mold, except for being a thousand times worse?

With Opalescence and Parallax Wave, I can get infinite card draw, infinite life, infinite tapped creatures (with Kor Hookmaster), infinite untapped creatures (with Volition Reins), while also creating permanent Armageddon (wherein all lands put into the battlefield go to the graveyard as a state-based effect when Enchanted Evening is in play, meaning newly played lands cannot even be tapped for mana once), while also countering all spells anybody ever tries to play, while also exiling all permanents, while also being able to protect my entire field from mass enchantment removal, as CrazyPierre mentioned, by exiling all of my own permanents with Glimmerpoint Stag.

With Opalescence/Parallax Wave, I am only susceptible to 1 card. Stifle. If you don't have Stifle, I get to do whatever I want to do for as long as I feel like it. My win condition is for you to deck yourself... I don't mill you, I just make the game hit turn 100+, and you deck yourself.

Turn 1: Adarkar Wastes, Sol Ring.
Turn 2: Mystic Gate, Parallax Wave.
Turn 3: [no land], Opalescence.
Turn 4: [no land], [at the end of the turn of the player before me and/or in response to threat to my field] Venser, Shaper Savant.
Turn 5+: Blink Venser with Parallax Wave to bounce all permanents in play, and bounce all spells played for the rest of the game.
Turn 12: death (for 1 player) by Venser/Parallax Wave beat down.

... you'd also need to give the artifact haste somehow.

Easy, with Parallax Wave, Opalescence, Enchanted Evening and an Azorious Signet, I tap the signet, exile it, exile Enchanted Evening, blink Parallax Wave, signet and E.E. reenter play, blink E.E., tap Signet, blink P.W., E.E. reenters play, exile signet, exile E.E.... and so on to infinite mana.

It may sound like some convoluted 4 card combo, but with Open the Vaults, Replenish, a few tutors, and so forth, it occurs fairly frequently.

Oh, and Enduring Ideal makes getting 4 enchantments into play relatively easy.

... You still need to give that signet haste somehow.

No I don't. The signet doesn't have summoning sickness when it isn't a creature.

In play: Azorious Signet, Parallax Wave, Opalescence, Enchated Evening
Step 1: tap signet.
Step 2: exile signet.
Step 3: exile Enchanted Evening.
Step 4: blink Parallax Wave [signet and E.E. enter play].
Step 5: exile E.E.
Step 6: tap signet (with 1 mana from the previous tap: net gain of 1 mana).
Step 7: exile signet.
Step 8: blink Parallax Wave [E.E. and signet re-enter play].
Lather, Rinse, Repeat
Infinite Mana.

302.6. A creature’s activated ability with the tap symbol or the untap symbol in its activation cost can’t be activated unless the creature has been under its controller’s control continuously since his or her most recent turn began. A creature can’t attack unless it has been under its controller’s control continuously since his or her most recent turn began. This rule is informally called the “summonings sickness” rule. Ignore this rule for creatures with haste (see rule 702.10).

Once I exile Enchanted Evening, Signet is no longer an Enchantment, therefore is no longer a creature, therefore no longer has summoning sickness, and therefore may be tapped for mana.

Step 5 makes it so you can't do step 7. If you've exiled Enchanted Evening, the signet is no longer a creature, therefore can't be hit with Parallax Wave's ability.

What you need to do is;
1. Float mana
2. Exile Signet
3. Blink PW
4. Exile EE
5. Float mana
6. Blink PW
7. Exile Signet
8. Blink PW
9. Repeat

Ah, I suppose you're right. All I have to do is change one thing.
In play: Azorious Signet, Parallax Wave, Opalescence, Enchated Evening
Step 1: tap signet.
Step 2: exile signet.
Step 3: exile Enchanted Evening.
Step 4: blink Parallax Wave [signet and E.E. enter play].
Step 5: exile E.E.
Step 6: tap signet (with 1 mana from the previous tap: net gain of 1 mana).
Step 6.5: blink Parallax Wave [E.E. enters play]
Step 7: exile signet.
Step 8: blink Parallax Wave [signet enters play].
Step 8.25: exile E.E.
Step 8.5: tap signet.
Step 8.75: blink Parallax Wave [E.E. enters play]
Step 9: exile signet
Lather, Rinse, Repeat
Infinite Mana.

Ahhh right. More convoluted, but doable.

The Opalescence/Parallax Wave combo sounds awesome, fun, and way harder to set up than Staff combos are.

All permanents have summoning sickness. It only applies to creatures, but if your signet is a creature, you cannot tap it for mana without giving it haste. Same deal as with Dryad Arbor or not being able to attack with a Glint Hawk Idol the turn you play it.

You're a little late to this party. I hope you brought beer, 'cause we're runnin' out.