This happened to me recently on my commute. Some roadies came up behind me and stayed pretty tight on my rear wheel for a few miles before I turned off. I wasn't about to disrupt my commute to slow down for them, but I was extra careful and kept checking over my shoulder because I knew they were so close. They had several opportunities to pass safely but stayed there for some reason. I think in that instance it shows a pretty clear lack of respect for a fellow cyclist, it's the same thing as tailgating in a motor vehicle. Pass asap or give some space.