I don't think I trust any web site in that regard, though. I could even see Google yanking the floor out from under me as a consumer of one of their URL schema.
If you didn't trust any web site, you wouldn't click on any link.
Trusting a website doesn't mean you have to trust them indefinitely. You can trust that the URL will be kept alive for a certain length of time - minutes, hours, days, etc - and deal with them accordingly.
