I have noticed that dynamically-user-generated pages, like search result pages , often get crawled by GOOGLE shortly afterwards, which is kind of spooky - I always guessed it was due to having Google code like Adsense, Analytics or FeedBurner on my page, and I quite like that anyway - free content!

But how does YAHOO do it?! I don't have any Yahoo code on my pages, yet I often get Yahoo crawling such dynamically-generated pages, even though they never make it into my sitemap and I can't see where they would get the link from. Maybe they are sharing data with someone else?