Disclaimer: I'm not going to be talking of the specifics of SketchFighter, in fact it's not something that gets out of the mothership, even for moderators. But the following provides an interesting background.
This is more than probably indeed some of the "secondary registration/piracy checks". You see, nowadays it's just not enough to merely put a big beefy "primary check" that the game has been registered, and not pirated. Even if it is made strong and well-hidden in the depths of the code, it'll always end up being cracked:
View Postfprefect, on Feb 1 2002, 11:18 AM, said:
It's only the most hardcore computer user who will try to reverse engineer the software and crack the copy protection -- and I'll be honest, there's isn't much a programmer can do to stop them. Crackers enjoy the challenge itself, the tougher the better, so that if they want it badly enough, they'll find a way.
A more subtle strategy is to still have the big primary check, but in case (or rather, when) it's cracked or fooled (thus removing the "obvious" registration block), then the pirate (who is definitely a pirate now, one way or another) encounters various problems because some or all of these secondary checks noticed some things were amiss. The advantage is that these secondary checks are not obvious, and more numerous and spread than the primary check, so it'll take somewhat longer for the cracker to crack them all. Checking through the 'Net that the reg code is a valid one (i.e. not one of the known pirated ones) when the program connects to the tracker for a MP game (it's not even opening a connection without your consent, I mean it has to connect to the Ambrosia tracker already, it's not Valve's Steam) certainly makes sense as a secondary registration check.