I understand startups may not have the personel to react as fast as a larger company with dedicated personel, and I understand that there might be a very large percentage of startups on Rackspace which might account for a nice chunk of revenue.
But what makes startups different from my personal website or a larger corporation? If Rackspace receives a complaint about a phishing site hosted on their servers, they should do what they can to correct that, regardless of which client is using the server that has the phishing attack. The startup should get the same treatment from Rackspace as the large corporation and the guy with some simple homepage.