I've noticed that there a couple of sites in Google whose ranks never change even though their content changes and Google spiders their site.
For example, the summary that Google displays for their site has been the same for months, but when you go to their page, the content is slightly different from the summary that Google displayed in the results. In some cases, the page is totally different.
And in one case, the owner has removed all the content and is redirecting Google to several pop ups but they still keep their rank and their old summary despite the fact Google says it has spidered the site recently.
Is this a Google bug or have these people found a way to work the system and make Google spider a certain page while showing another? It's frustrating and doesn't seem fair if they are cheating.