As a Rule

Sometimes I see someone qoute a 'rule of thumb' and I wonder: Whose rule and whose thumb?

I don't know where that thumb as been. Why would I heed it?

For all I know that thumb could belong to a complete degenerate given to late-night trolling in seedy parts of town for loose women and cheap booze or, say (just a wild and crazy thought here) it could belong to some stick-up-the ass blowhard pendantic.

Rules of thumb in writing are almost always presented in such a way as to make me want to punt them halfway across the room.

**edit to add:

Now that I don't feel so ranty.... I think when some folks say 'rule of thumb' when giving writing advice they really they mean 'generally speaking' 'try this'. Then they compound the problem by using RoT with some variation of an absolute--ie: As a rule of thumb the hero and heroine should meet by page 5. As opposed to: Generally speaking you should have your hero and heroine meet as soon as possible.