I find the spines pretty avoidable. Ive never gotten seriously injured by any of them. Phoneix palms have thorns that will hurt if you touch them too much. Livistonia also have thorns that can be dangerous, but if you take care not to rub against them, you'll be fine with those too.
You can cut off the spines if you want to. It wont to any harm to the palm as long as you dont cut it too far back (and damage the stem). I cut off the spines of my European fan palm and it seems fine to me. I also did it to my Livistonia a while back and it also was okay.
-Alex

The first step we do every year for commercial date growing is trim all the thorns off so we can get into the palm to work it. we use a knife that looks like a carpet or linoleum knife, only MUCH larger. For a couple of palms, a carpet knife would do. use a diamond rat tale to keep it sharp. Trim the thorn right at the base of the thorn, just before the rib of the frond.

Has anyone every cleaned the trunk of a needle palm or pruned it back to a single trunked palm?

funny you mentioned- just transplanted and removed a few babies/pups off a huge 7' x 10' needle palm that was planted in the mid 1970s as a baby! the needle palm is huge and beautiful and seperated fine- Justin in Vb