And by the way, before we get into a discussion of practicality and "impact," I'd like to note that the Libertarian candidate will be in the presidential race long after Ron Paul has taken his unspent millions and gone home after losing the GOP primary -- unless he's planning to *really* be a politician and flip-flop on his promise not to run for office if he's not the GOP nominee.
So those of us who are committed to the election for the long-haul, and not a flash in the pan, have a candidate that we can back while rigorously applying all the logic of the Ron Paul crowd -- as well as a nice big dose of real Libertarianism.
Further, the former LPers who have quit the party for the GOP cannot do a blessed thing about it, even long after Ron Paul has quit the GOP primary.
Goodness, we might just run a good race! 
Cheers,
Brian