Quora is from Mars, Instagram is from Venus
Quora and Instagram have both been rocking my world over the past few weeks, for very different reasons. Both provide incredibly intense community experiences. Both use other services to some extent parasitically. Both should - arguably - have been built by existing services (Twitter should have built Quora; Flickr should have built Instagram). Both are much discussed and debated, and growing rapidly.
But that's where the similarity ends.
