I'm not entirely sure that pawn shop customers fall in line with Bitcoin's tech savvy libertarian demographic.
However, there are many who would not normally visit a pawn shop but would if only they know the proceeds would be provided in bitcoins. The advantage to the pawn shop operator is an increase to inventory of more valuable items. They don't need many boom boxes but jewelry or a nice commercial electric drill and now the operator might become interested.
Incidentally, I did speak to a couple of pawn shop operators. Until they have customers coming in asking if items can be pawned in exchange for bitcoins, they generally will be less than enthusiastic. But just like how the UK Copy Writer learned that being the first supplier in the industry to accept bitcoins gives an advantage over the competition ( http://www.ukcopy.co.uk/blog/2011/11/the-amazing-power-of-bitcoin
), the first pawn shop to do this will likely find it to be worth the effort.