They seem like decent enough projects for fun. But anything long term might be slightly tricky. I particularly liked memify.me and it seems like it could catch

They seem like decent enough projects for fun. But anything long term might be slightly tricky. I particularly liked memify.me and it seems like it could catch on. leftright, as someone had pointed out, seems similar to what's been done. An extension of leftright could be including some sort of question for people to guess - could be age, location, etc.