I guess I'll live with parking charges at places like the Mark Hopkins in SF, in Central cities, etc., but I guess my least favorite parking trick is the mandatory parking charges where the hotels have conspired with the cities, and/or local homeowners/businesses to rip you off: Take the Glendale Hilton, for example, in LA.
Glendale has PLENTY of on street parking, and the hotel is in a big open area. Every business around it has the lots posted for towing, the city offers NO on street metered parking (even though the streets are fully wide enough for multi lanes and left turn lanes etc., and all the residential/business neighborhoods are posted as towing 3am-5am. Thus, your only choice is the $15 hotel parking, when there are literally HUNDREDS of parking spaces empty within 1 block, and THOUSANDS within 5-6 blocks, a reasonable distance to walk in a "safe" city.
You can probably cite dozens of examples identical to this if you travel on business. The Hilton Burbank and some of the Woodland Hills hotels come to mind in LA.