Daily changes and large updates - whats the difference?

[eoinm]

The sites I optimise change ranking (in a small way) on an almost daily basis. Sometimes they're #3 sometimes #4 and so on. As I said, this happens on a near daily basis and when I check my logs I see Google crawls my sites every few days.

So the logical conclusion is that Google slightly alters my position based on these crawls. Which is fine.

However, what I'm curious about is the difference between the above normal behaviour and one of these Google 'dances' that people talk about? If I see a shifting in my ranking very regularly how is it possible to tell when a bigger movement is happening?

And, just out of curiousity, who names these dances (jagger etc?)

Thanks.