Got a shock last night after the cron job ran to update all my keyword tracking in DP's tool. Many of my top rankings were gone, but on closer inspection google had switched to ranking them under an old domain I have which for lack of anything to put at it right now, I had aliased to my primary site. I immediately put a 301 redirect for the entire domain in the apache conf file. At least people will find me from search results still, but I'd like to start using that domain for some aff. marketing soon... Anyone have thoughts on whether Google will fairly quickly revert to showing my main domain for the SERPs? I wasn't out to trick the SEs or anything, I just had a few different domains defaulting to the main site until I had something to do with them. Turns out this one is a good seven years old, has a PR6 and has been in google's index for about as many years, though the original content no longer exists.
Funny, something like that happened to me when I registered a bunch of domains, since they were all being forwarded into the main site anyway it did not matter to me, but Yahoo had them indexed funny for a long time showing the domains that were being forwarded into the main site instead of the main site. Since then they have reverted to using the sites main URL.
For several of my main keyword phrases it kind of varies between which site comes up first, but both are generally in the first two pages at google. There's one case where the rogue domain is #1 and my main site couldn't be found several pages down.
Not much you can do about it other than point everything where you want it to go and hope they index it right down the road.