Honestly, it depends on what you mean by 'look up' - Coffee Meets Bagel (another dating app) includes a feature that will show you mutual Facebook friends (if such a thing exists). That's a really interesting indicator how/where a match's social circle overlaps yours, which can say a lot of important things. That totally ignores, of course, the opportunity to get a second opinion from one of those mutual friends as well.

Stalking and/or looking up 13 year old college party photos is probabally, shall we say, less sane.