PS3s have been sold out consistently in my area since about a week and a half before Christmas (which is something I and others have been saying since that time, yet many often ignore it).
They aren't withholding anything for anything. They're simply struggling to catch up to the demand built up before Christmas.
Wiis are sold out for a similar reason. This was the biggest holiday yet for both consoles, and for the ps3 it was its biggest holiday immediately following a massive spike from the launch of the Slim. Upping production to meet seriously increased demand can be troublesome, especially if you're Nintendo who actually decreased Wii production earlier this year.