I guess people keep bring it up because they think it's funny or think it makes them seem cynical, but it would be a mistake to think Snapchat is primarily used for sexting.
I don't have any data either but I think comments like op above are really trying to legitimize a sexting app. Lets take the recent Tumblr acquisition. Most tumblr blogs involved porn although they were able to legitimize is it as a better blogging service.
Seriously, of all the users of Snapchat that I know, only one of them is a reddit user as well.
Statistics 101.
This is blatantly false. It was estimated that about 10% did. Porn was never the biggest draw of Tumblr.
I was really hoping it would be a link providing evidence to one side (Snapchat is primarily sexting) or the other side (only a small % of snapchat usage is sexting).
You can't really have much more than anecdotal evidence at this point, so I offered this.