Last year we stayed at the Hilton on Marco Island and they had a daily "resort fee", which covered use of the pool, beach, etc. It was about $7 per day- plus tax, probably- and was added to the room rate and was not discretionary.

I accepted it at the time (was still cheaper than the rate at the Marriott, the official site of the meeting I was attending), but I agree that it's better to write and complain. If it's involuntary, it should be in the quoted room charge.