I was reading a couple of months ago that that issue was being addressed (I believe on a WEVA post).
In Australia, I was told pro videographers pay a $600 per year fee which allows them to purchase music (CD, Download, other legal mechanisms) and then include it on a per project basis (less than 10 units delivered, non-braodcast). I believe such as mechanism is being looked at the in the US.
I could be wrong - I am not a lawyer, nor do I play one on TV.
Until that point, you have three options -
1) Acquire the licensing (lots and lots of $$$$$$$$$$$$$$$$$$ - very few do this)
2) Use it and hope and pray you don't get bagged (many videographers do this)
3) Use royalty free music - There is some very good stuff put there for NOT an arm and a leg plus there are packages like Cinescore and Sonic Fire Pro which make this easy and affordable.
Good luck in whatever decision you come to.