I suspect they'll find out for themselves. :)

However, if you want your site to do well, you may need to think about how searchers will find you.

What do you mean?

If your pages change constantly and are "so dynamic it's probably pointless", then surely you are saying that you believe that they are not indexable?

If it's the occasional index like WebmasterWorld, don't worry; but if it's content pages, then you have a potential problem.

You can direct SEs not to index pages that you don't want to be indexed, but don't worry about whether they *can* be indexed or not - that's the SE's job, and you wouldn't want to stop them indexing a page that could be indexed - and if it cannot now, that doesn't mean the SEs won't have learned by next week!

And never underestimate the SEs; Google used to index new pages every three months; now some pages can appear within an hour of creation.

Let them do the worrying!

If a significant proportion of hits will be based on searches for content that no longer exists then that might damage the brand image of your site. That would be a valid reason for making a page "noindex".

That is a decision for you to make.