Quadrille - 1:56 pm on May 4, 2007 (gmt 0)

It would confuse them.

They compare the page in front of them with the one they've cached. If there's a significant change in what they find, they might well treat the page as a new one.

Even if they took your word for it, their index would only hold one version (the 'latest' one spidered) - so most of your searches risk being wasted, as the spider won't see most of your content when they visit.

Say you have five 'revolving messages' - at least four will not be indexed. Maybe all five. Weird to hide content from visitors; suicideal to hide it from SEs.

Place each item on its own, linked page, and it will be spidered. And seen by visitors.