Working where I do, you see a lot of dirty lorries and vans. Why do people always write "Clean me" and the like on them? One time I saw "All I want for Christmas is a clean", which is really tugging on the heartstrings to an unnecessary degree.
The thing is, nobody writes "Clean your van", or "This lorry is really dirty". It's always first-person, written from the point of view of the vehicle. I suspect that the lorries exert a hypnotic influence over passers-by, and compel them to write these messages.
Note - I saw David Cameron and Nick Clegg today, and the above is the most important thing I can think to write about.