Manyshot specifies a single target, though; it's a special case.
For other cases of multiple attacks (whether from BAB, Rapid Shot, or whatever), you don't even need to specify your target until after you've seen the result of previous attacks. If I have three shots with my longbow (BAB +6/+1 and Rapid Shot, say), I can shoot one arrow, see its effect, then decide whether to shoot my second arrow at the same target or a different target, see its effect, then pick a target for my third arrow.
-Hyp.