I've got a *few* comments to add:
First regarding why go to SFO: I thought the very same thing. I mean, Villian is good no doubt, but it rides very similar to GAm's Viper. I guess though you could still go there for B:KF and Big Dipper.
Second regarding noise concerns. If you dont live near a park, you are really in no position to comment about local concerns. And as far as people just selling their house and leaving, who's gonna buy it? GAm has plenty of space so there is no *need* for them to buy it. And, as has already been pointed out, who would buy property by a park. It's a catch-22.
On the capacity issue, I doubt that adding the two coasters is going to have much more effect on the crowds as adding just one new coaster. So while the lines for these coasters may be long, i would expect the other lines to drop a little.
As for the 3-trains on RB, most times they do run three. BUT I went there on a Sunday this august and they one ran two (coincidently, they only ran 2 on Shockwave as well...but all three on Demon hmmmm).
Finally, there are only 3 existing invertigos worldwide (PGA, PKI, SFA). You are thinking about the thousand and one boomerangs on the globe; simlar, but different.
lata,
jeremy
---Six Flags Great America, the only park in the world where you can swing your feet on FOUR coasters!!!