How many band members is optimal?

[beerrhino]

As few as you can get away with

[mawso]

As many as you need to properly deliver the material, and no more than that

That might be 1 or it might be a whole orchestra

I prefer power trios to the 2 guitar and separate singer-type bands i was in when i was younger

[Discö Rice]

I can't really see myself working with more than one other person. I don't have the patience. Maybe if it was the right group... Nah.

[+--Stonah--+]

The fewer the better.

Exactly right 

[Mike IQ]

The more the merrier. That way, bills are split up among more people and if one person flakes out and leaves the band for any/no reason, it is less of a hardship. I'm going through this right now with our guitarist quitting out of nowhere and this is the umpteenth time this has happened to me and I really resent it. I'd rather have two guitarists for that reason.

Also - and not only because I'm a stand-alone singer - I don't think singers are less likely to phone it in if they are also playing an instrument; if anything, they're more likely. I've played bass and sang at the same time and it's hard to put in the same energy level when you're doing that as you do when you're just holding a mic. If your singer sucks, it's not because he doesn't (or does) play an instrument; it's because he sucks.

[Lumpy]

Also, more people = more people to help carry shit. I was in a 2 person band (now three people) with a guy who has a bad back, and can't really carry anything (or pay for anything). More people to help load equipment is nice. Two people can be a little severe, if there are stairs involved, bad backs/knees, alcohol, etc.