What's the difference between a Triple IPA and a Double IPA? One of the recent trends I've noticed is that breweries are starting to come out with Triple IPAs. (In fact, there's a triple IPA week in the Seattle area.) But what exactly distinguishes the Triple IPA from a Double IPA?

[Note that this was not included in IPA and variants question, nor is it discussed in the IPA vs. DIPA sweetness question.]

Edit: This is decidedly NOT the same as the question regarding dubbels vs. tripels (which are Abbey-style Belgian ales, and remarkably different in style from a double or triple IPA).
A bit obvious, but it's just about more malt and hops (which results in higher ABV and IBU levels, off course).

Particularly, I don't see it becoming a new style, as our palate has a limit when it comes to tasting bitterness and even smelling hop oils. I think we have already reached this limit sometime ago when Imperial IPAs were conceived. So, anything beyond that seems like a silly obsession to me, and probably the best that one can get from a "triple IPA" is to come up with a good Imperial/Double IPA with (maybe) more alcohol, nothing more.

PS: Dogfish's 120 Minute IPA would be a quadruple IPA, then?