Rackshack have posted to their support forums that their power consumption has hit the limit of the local Houston power grid.
Rackshack expects to have a second datacenter, also in Houston, but on a different segment of the power grid, in the first few days of September, and that [at the time of the posting] it had around 600 servers available to rent in its existing datacenter. 600 servers sounds a lot and more than the entire installed base of many hosting companies, but Rackshack is one of the market leaders in Linux/Apache dedicated servers and has been adding in the region of 1000 new Linux servers per month to its network.