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]
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...