I own nearly 30 domains on GoDaddy. I use another tool to check domain availiability but GoDaddy is my main domain registrar so if I do check something there I'll almost certainly buy it. This pattern must've flagged me somehow, because lately if I check a domain but don't buy right away, it is gone the next day. It happened THRICE in less than a year and is very fishy to say the least, because the domains are not even popular keywords and always longer than 10 characters.
So yeah there's definitely some fuckery going on.