I guarantee there are a few folks (or even a lot?) that switch back and forth for the reasons you've described. However, you should realize that many, if not most of the "side-switchers" are NOT doing it for those reasons.
Personally, I switch teams all the time. I log in, look at the #'s and the available fights, and almost always switch to the team with the fewest players.
On one occasion, I switched to all three teams on the same night. If I'm on a team that isn't giving me access to decent fights, I'm gone. Or if my team begins to swarm over another...
Personally, I hate being on the team that is outnumbering the others. I hate having to fight my teammates to get a kill.
Startegy? I don't care a bit. I'm in it to shoot the red guys. Even if they were green a few minutes ago. The last thing I want is to capture a base. I've even been known to steer my countrymen AWAY from CV's that I or a squadie have located. Kill the CV and wreck the fight? I think not!
Hmmm, I suppose that's kind of the same thing as spying, huh?
Never mind the above, then!
MtnMan