Haha! Nice monetisation idea! We just have 'Yarrly.com' - going for high viral-coefficient first, but not going to overpower people's output with advertising/watermarking --> USER FIRST! ...but we'll keep it in mind!
Sure! This started as a learning exercise, so to get the maximum learning, CHOOSE WHAT YOU DON'T KNOW AT ALL. (No really.)
So Android, (full disclosure: I've done a bit of Java, I'd rate myself as not beginner but nowhere near experienced). Android is hard to develop well for, it's activity lifecycle took a long time to get my head around, and once I hit real-world testing with different devices it was just a roller-coaster of debugging that was highly, highly challenging. Also, everyone is doing things iOS first, and that's boring. We wanted to give Android users an awesome, fun, show your friends app that was hilarious, silly and pushed things forward, even just a little.
Nodejs - I'd wanted to do something in anger with node for ages, and this was the perfect opportunity. Also no proper nosql experience, so mongo!
Full disclosure: It's on top of heroku, to save time.
Id like to say there were more deep seated reasons, but they are the most honest - try something you don't know, then just focus focus focus until you nail it.
Love to port it to iOS, of course - but that's a whole NEW learning experience. Let's see how we do android first!