I clean virtually every dirty chip I buy. I can live without those germs, frankly.

Additionally, like it or not, it is irrefutable that a clean chip will ALWAYS (100% of the time) sell for more than a dirty chip in like condition. That being the case, I would say that if you like dirty chips then by all means collect them that way, but if you're looking to sell chips, you should clean them. The dealers know this, by the way. Doug Saito, for example, cleans virtually every chip that he sells. The difference between chips and coins is that cleaning a coin will alter its condition (considering that lustre and toning are part of the description of a coin) while cleaning a chip will have no effect at all on its condition.