In January, my wife was driving our rental car in the Palm Beach area, inadvertently missed the "exit" to get to the manual toll lanes, and had to drive through the high-speed EZPass lanes. There was a sign there with a phone number to call if you went through the toll lanes without a transponder (they gave us 10 days to mail in a check for the toll to avoid a fine).

FL also has a system (see www.platepass.com) that will charge the tolls back from many rental car companies to your credit card (with no penalty but with a ~$2 per day service fee for each day the rental car uses the transponder lanes). You can actually check your your rental car agreement number on the web site to see if your toll got picked up that way.

By the way, my favorite toll-taking "enhancement" is the removal of the manned toll booth coming off of I-294 into O'Hare. There is no advance warning that your only option (if you don't have an IL transponder) is to put coins in the exact change machine. Given the large number of rental cars that go through that toll interchage, I have to wonder how many folks are either having to mail in checks (or paying the fines via credit card for not paying the toll) every day due to that interchange.