The answer to whether the U.S. should act depends on what we are intervening for. For example, delivery of humanitarian aid to the thousands of Libyans and expatriates trying to get to safety, either within Libya or across its borders, is probably feasible with little risk. Opposition forces would not get in the way and regime forces have their hands full just securing Tripoli, let alone retaking nearby towns or the cities in the east.
Logistical obstacles, however, are another issue. Are the refugee clusters near airports that can cope with modern military cargo planes? If not, what are the practical difficulties involved in getting assistance from airports or seaports to refugees near borders over very long and exposed road networks? Mundane issues like these can be nearly as much of a barrier to humanitarian intervention as military resistance. Nonetheless, U.S. and allied forces have a great deal of experience supplying aid in very challenging settings, from Haiti to the Congo, and would undoubtedly rise to the challenge. Moreover, help for innocents in distress is a moral duty that Americans take seriously.