One important factor to consider is scalability. A lot of people like to launch with a relatively immature server that only supports a relatively small # of people in a beta with the idea that they will expand it after that # of people come in. I think this adds an extra risk of someone absorbing your ideas and it's better to get a nice, horizontally scalable server. You don't want to break on slashdot or techcrunch and then have the site go down under load.