It is possible to create a "good" startup with a "good" idea, but "great" startups are often the result of ideas that would have seemed ridiculous if you had heard them prior to seeing them working. This is true almost by definition - if they had been so obvious, lots of companies would have already been doing them.
Ask yourself, if you were a venture capitalist pitched one of these ideas, what would your reaction have been?
For me Facebook is the most ridiculous the world needs yet another social network a la Myspace or Friendster except several years late. We'll only open it up to a few thousand overworked, anti-social Ivy Leaguers. Everyone else will then follow since Harvard students are so cool.
What do you think about AirBnB. Why would anyone let a complete stranger to share a room in his/her house? Ridiculous. That stranger could be a paedophile, narcotic, felon and god knows what. But you know, it is successful.
I have theory on why it is successful. People looking to make extra money during the 2008-2010 recession wanted an easy way. They already have their homes and there are travellers always. Why not make money without doing anything? And it worked. I know people who bought condos during the housing bust in the vegas area just so they can rent them out on AirBnB. This idea is not new. There is VRBO where owners have been renting out vacation homes for a long time even before AirBnB. But, AirBnB commoditized it and the network effects kicked in.
twitter: most silly invention, ever. Share 140 characters while other social networking websites allow to post anything and everything o.O
Snapchat: While every other photosharing apps let them store their favourite pics, Lets destroy them in 10 seconds.
instagram: We will use phone's camera, few filters and deteriorate the photos uploaded before sharing. How cool it is. o.O
There are many more startups which are ridiculous and I guess it just need an idea and people to work on it and the most important thing is you should master the way of presenting your work to people to become a successful entrepreneur. Thanks.