Maybe this is a dumb question, but when you put glue on the tube, presumably you want to use a little too much, to ensure that all of the patch is sitting on glue. This means there will be a little glue on the tube around the edges of the patch. What is the risk of that circumferential glue causing the tube to bond with the inside of the tire, so that you can never get the tube out again (without ripping it)?

I've never had this happen, but I don't understand why not. Do they make the inside of tires so they are not chemically compatible with patch-glue?