Startups must be sponges
Wednesday, November 14, 2007 by Dave Winer.
I posted this on Twitter, it's worth posting here too. 
You'll never make your product better if you shut out all criticism. You have to iterate to hit the sweet spot.
I don't often say people are wrong, I'd rather say products are flawed, or companies make mistakes. But companies that try to shut down critics, with personal attacks, are wrong. Startups that do it are worse than wrong, they're doomed.
