wappr, from Netizens Media. I'm blogging this simply because it's come up so many times that I'm sure it'll come up again. I've never thought this was a good idea, but I've heard it suggested by many people many times. (By the way, if you've suggested this to me and I've nodded as if I thought it was a good idea, I have to apologize for misleading you; I was only being polite.) I can see how it might be entertaining to build, and useful to share in private among a very small group of very carefully chosen people - for instance, your co-workers at a great company - but I can't imagine why anybody thinks this makes a good app for a large audience. Startup success is rare; ideas without execution are valueless. An app of this nature is a system for harvesting items of no value, and it is difficult to create value by harvesting and cataloging items of no value. You can't make it up on volume.
You can see from visiting the site that most of the ideas are trivial and/or ridiculous. These are the three most popular current app ideas:
1. I wish there was an app where you could report a car whose alarm has been going on for hours, and car thieves will read it and steal the car
2. I want an app that I can play where I destroy everyones farmville. Like unleashing locusts or severe droughts.
3. I want an app that passively records an evening's conversation and then turns it into a tacky powerpoint.
Obviously, this is fun, but you're not going to make a million dollars with it.
For the record, this is not incidental; it's inherent to the economics of participation, and guaranteed to happen for any such app, in the same way that trolling and groupthink are guaranteed, by the economics of participation, for Hacker News/Reddit/Digg-style community-upvote aggregator sites. Contributing ideas without contributing work is very, very low-cost, and the likely payoffs - people dissing your idea, or praising it and then doing nothing about it, or praising it, building a startup around it, and failing to get anywhere with that startup - are likewise minimal. Consequently a system of this nature will attract only people with time to waste, and not even people with lots of time to waste (who tend to do more interesting things with that time than people who only have a little).
Speaking of no time to waste, I've got to wrap this up; I'm late for something important to me. Long story short, I think it's very important to look at the economics of participation when evaluating social software. I've worked for a few startups, seen a few do well, seen one do very well, seen several fall on their faces atrociously, and noticed some patterns. I always look at the economics of participation, and I think everyone who wants to build a startup around social software should do the same.