Steve's 100% spot-on here. I don't have bogon filters at all and it hasn't hurt me in the least. I think the notion that this is somehow a good practice needs to be quashed.
Some people don't use condoms with hookers either. Just because they haven't caught anything yet doesn't make it a smart practice. Sorry I have to agree with Steve as well. I know I've left networks with Bogon lists in place and then gotten calls a year or more later asking why
traffic can't isn't coming in from XYZ new client. Turns out the new admin never updated the bogon list. If this was done through a central repository and updated daily, or required the list to be refreshed periodically otherwise it timed out- fine. The problem is people leave these lists in and forget about them. If you are going to keep on top of them, and make sure to remove them when you leave- then that's great. But if you are going to do it half way- please don't bother. -Don