[jcfausto]

Good points! These arguments leads us to the point that we don't need to give up on some idea just because it is too simple or is something that already exists in the market. Although sometimes it's really hard to go on over some idea that already has a strong and stablished competitor in the market.

[rpedela]

Yes that is true. I would add that typically most startups attack a particular niche first before taking on that strong competitor. A niche where that competitor is weak or absent.

Some of the best advice for you question is from Paul Graham: http://paulgraham.com/startupideas.html