We'd love to have an airsoft arena in the bay area... The only place we can really go that is close by is Operation Paintball in Hayweird... It has a small indoor arena which is pretty cool, but it's very small.
I think that if someone opened an airsoft arena (a big one) somewhere in the heart of the bay area (near fremont-ish) that they would make a killing $$$.
I've been pondering this myself, but I have other projects that need to be finished before I venture out on a limb... I'd also need some business partners.