I'd never heard this phrase until a couple years ago and then I started hearing it and seeing all over. Is it just me or was there some kind of...sea change?

Hmmm. I can't say that I've noticed that use of the phrase is any more common recently. I'll keep an eye open.

I do think it's much over-used these days. Though Fowler complained of it as a cliché in Modern English Usage, I hadn't been much aware of it till recent years.

It's usually used just as a synonym for 'change', which is utterly wrong: effectively a misquotation. The original context is a very special, slow kind of change: those are corals that were his eyes; nothing of him doth remain, but hath suffered a sea change into something rich and strange. Stripping the phrase of this imagery makes a mockery of it.

My sense of sea change is that it need not be a very gradual transformation -- though it certainly was in the instance aput cites. I read it as a thorough and complete change, not abrupt but not necessarily slow either.

I think that's equally in accordance with the Shakespeare's passage. There the change was very slow -- but Shakespeare's point is that it was very complete. Let me quote a bit more than aput did.

Full fathom five thy father lies;
Of his bones are coral made;
Those are pearls that were his eyes:
Nothing of him that doth fade
But doth suffer a sea-change
Into something rich and strange.
Sea-nymphs hourly ring his knell

I had always thought it to mean "profound change," though I suppose a profound change takes time. Quinion has a similar point to aput's about it being used wrong. Apparently it began to be used in the late 1900s. In Shakespeare's original quote there was a hyphen, though modern dictionaries don't have the hyphen.

Hm - I've never heard it used in conversation. I might try it out this week and see if anyone around me knows what the heck I'm talking about. I love doing that.

Langauage Inflation:
I suppose that we can't just have changes anymore becuase they have to be sea changes, just like we can't just have benfits anymore, becuase they have to be real benefits.

Hm, I give myself 7/10, not too bad I suppose for one of the few occasions when I can't be bothered to look a quotation up. 'Remain' for 'fade' is interesting: I don't understand what 'that doth fade but...' means, so I re-engineer it.

I am impressed, aput! I would have to give you a 9.99/10.