I think that Mark makes a lot of good arguments about the viability/desirability of RPGA events at Gameday. Lords knows I don't know jack about RPGA stuff, so I'm happy to defer to his wisdom.
Ultimately, however, I'm happy to see Gameday host whatever events local ENWorlders want to run. That's really my focus: this particular online community. E.g., I wouldn't want to seek out some RPGA folk to run an event just to bring in warm bodies (Mmm... bodies...). I just want Gameday to be an event where ENWorld locals (and not-so-locals) can get together, play some cool games, make new friends, and buy some swag. Whether they want to do that under the aegis of the RPGA or some other organization is fine by me.
The RPGA fee issue Mark mentioned, however, is sort of a sticky wicket. Still, I'd guess players would be aware of that going in.
As with good gaming in general, the prime directive of Gameday, as I see it, is simply: Would it be fun? If so, let's do it.*
*As long as it does not harm the person or property of a non-consenting other, of course.
