that is a problem for instagram - it isn't defensible atm. I imagine the Android team will look at it and think 'really, so people want to do that - ok, lets add filters in the next release' and done.
The filters are part of it, because of the way they gloss over crap/boring photos with a layer of nostalgia.
But there are plenty of camera apps on the iphone that have filters (often exactly the same ones) and can post to facebook/flickr/picasa -- and they haven't generated the interest Instagram has.
There's more to it, and it really does seem to be the social-network-seeing-what-your-friends-doing part.
I know, I wouldn't use instagram or these filters anyways, but people seem to like this hipster stuff. Bigger problem for them is, they have to think what to offer their users before these vintage-effect photos stop being trendy.
Ehh, they don't have to worry about that until the cameras on phones stop being so shit. The reason people like the vintage effects is that lots of phones end up taking blurry, slightly out of focus, under and over exposed photos. Slap some vintage filters on that and it looks somewhat charming.
Now, on the other hand, take some serious optics and truths same and unless you explicitly start blowing things out on the photo you've got something weird and artificial looking.
