Ideas For Your Next Startup

The new news aggregator: Bradford Cross[1], founder of YC 09 FlightCaster, is giving his shot at this with GetPrismatic[2]

[1] http://www.crunchbase.com/person/bradford-cross

[2] http://getprismatic.com/newsfeed

No. 2 has been done a lot and is very hard to monetize and scale? There's a lot of people tackling 3 and 5 (including tbe aforementioned pinterest) and 3 doesn't seem practical/useful at all, imho...