That's the big use case right now. A more flexible version of http://www.quickmeme.com - though I'm sure users will come up with other cool uses in the coming months.
The "let's put captions on pictures" fad surely can't last forever. It's still only five years since the first lolcat, and the super-meme here has acquired hundreds of mini-memes (lolcats, advice dog, courage wolf, yo dawg, FAIL, philoso-raptor,... and a serious bunch of crap that's probably hilarious to about six dozen people in the world). Anyway, it surely has to get old eventually... I can't imagine that my kids will still be captioning things.
Lolcats may not be forever, but captions are. So are people who think they have comedic talent. Make a great online photoshop option, and there are many options.