Let me say right up front, I also play guitar and think all bass players should play some guitar. Whenever I hear someone putting down guitar players I assume they're not professionals and most likely young teens. I will also admit -- if a guitar player never played bass, he'd be able to play some songs on a bass, whereas if a bass player never played guitar, he would not be able to play any songs on one. That's just the way it is. But here's the kicker -- Assuming most pop tunes are written on acoustic guitar, there are essentially 3 basic rhythm strums that are used. But there are hundreds of different bass patterns. When writing music, the bass part requires more thought if the song is to "come alive." In cover band situations, a guitar can just lay out or play percussively over changes he doesn't know. The bass player has to know the song! And in a jazz context, the guitar can throw in little comps here and there, but the bass has to outline every beat, and make it swing! That's just a couple of examples . Can you think of any others?