This panel is lifted from a slightly longer Commit Strip cartoon but it sums up, beautifully, the reality of start-up culture and why the emphasis on small “disruprive” companies is so misplaced.
The point to bear in mind when discussing start-ups is that these are companies, operating in low-risk environments, randomly chucking stuff at the wall to see what sticks.
If you want to develop yet another social media silo, feel free to found another start-up and good luck to you. If you want to write software that people are going to depend upon, you need to do it properly.
For an example of what I mean, go read Charlie Stross’s take on the Mt. Gox collapse.