I have no idea about other technology sites, the only one I'm aware was hosted by them before us is hardocp. The Planet is really a HUGE host right now, and I know for a fact it was a growing company when we got them to sponsor us, but nothing like it is today (and we are proud to say it).
They recently merged with EV1 servers who are also big (compared to The Planet probably bigger in numbers but not in reputation), so the combination makes for one of the biggest hosts in the whole US.