470 around Denver, going out to the airport, takes pics and then bills you through the mail. All of a sudden one visit the pay booths were shuttered up and out-of-staters had nowhere to pay in person.
As a constant traveler, I didn't even know the bills had arrived at home, and when they weren't promptly paid (usually under $5ea if I recall correctly) a Late Fee and other crap was added on, for EACH toll gone through. Ended up being like $35 for each time, over a couple hundred total in fines and late fees, for just one visit to the Denver area.
I refused to pay it, let them know their online pay system was lousy and non-functioning, and suspect that a lot of people did the same. They eventually let everyone know you could pay the original toll and a relatively small fine and all would be good. It was a real mess for awhile.
Point is, with SunPass or other places that snap an image of your plate and then send you a bill in the mail, it's best to get it taken care of to avoid potential hassle down the road.