If you've ever drank water (or even tea) at a restaurant, it's not uncommon for the waitress/waiter to ask if you would like a lemon. Next time... stop and consider this!
ABC News conducted a study of the 10 germ filled places in a restaurant. When the lemon wedges were swabbed, HALF were tainted with FECAL MATTER! (aka- POO!). Their cameras caught employees grabbing lemons with their bare hands, and if they hadn't washed their hands correctly, it makes sense why the lemons would contain fecal matter.
Another study found lemons covered in microbes and other bacteria- including E. Coli!