I tailgate people so badly.
On the highway I have found it is a good way of getting people who are doing less than the speed limit or ignoring the 'keep left unless overtaking' rule to get out of the way. I have no sympathy for people doing less than the speed limit in the right lane. I'll drive 2 metres from the back of them until they get out of the way or until I get impatient enough to start with the brights flashing and horn.
It doesn't really help on single lane roads but I do it anyway if people are going too slow because they piss me off. If someone is going a fair bit under I also tend zig zag around behind them so I can look ahead and find an opportunity to pass. I don't care if it is a residential road I'll pass them anyway.