Who are you this time?

I just noticed something strange about Google Secure Access. I'm at Den Haag Telecom, listening to a UPC presentation in Dutch, I have also been playing with the laptop. I noticed that when I go into my blog site through my Sitemeter tag (which necessitates log-in, which is how I know it's me when I check the IP address) it comes up as this, though last week in London it came up as collation.net. Both are underpinned by Cogent Communications' IP address, but I don't understand why apparently totally unrelated companies should turn up as my alias. Martin thinks it's something to do with errors in DNS reverse lookup. Has anyone else noticed this sort of thing happening?