I guess my question was two-fold... firstly if a spell fizzles when one of several targets becomes illegal or nonexistent, and secondly the order in which the Ghost's ability and the resolution of my Bounty occur. Indeed a multi-target spell will resolve if at least one target is legal and exists at resolution, according to:
http://wizards.custhelp.com/cgi-bin/wizards.cfg/php/enduser/std_adp.php?p_faqid=138So I guess I should have checked the Knowledge Base first. Thanks for the reply though!
Regarding the order, the Ghost says "When Skulking Ghost becomes the target of a spell or ability, sacrifice it." The key word there is "When". "When", as well as "Whenever" and "At", denote triggered abilities, which trigger when(ever) the specified event happens or at the specified time, and go on the stack the first time a player receives priority after they trigger.
Since you receive priority after playing a spell, in this case the bounty, the ghost's triggered ability will trigger while the bounty is still on the stack and will go on the stack on top of the bounty. As LordHomerCat said, this means that when bounty resolves, the ghost will be gone. The bounty will, as he said, do as much as possible, which is giving the bears +2/+2. As LordHomerCat said, things will happen as you want.