I have used Highbeam, an online research service sporadically over the years. Once you sign up for this service, you will keep paying and paying until you tell them to stop.
I just got notice that I was signing up for another year -- for $100 more than 2009. I was even billed for a credit card that didn't even come close to matching my number. But AmEx honored it.
Back to HB -- when I cancelled online, I was given an offer to save $100 if I stayed as a customer. I declined just wanting to leave the service and save the money.
But I found that my card was recently charged and the company doesn't give refunds. So I still have service through next spring.