Backbase.com is one of the web sites that is using two versions:
Note: You cannot open the "search engine" version directly, use telnet.exe or the Google cached page at http://220.127.116.11/search?q=cache:pVNGuQ5tDvAJ:backbase.com/go/home/company/news/008_ohra_backbase.php++%22u%22+site:backbase.com&hl=de . If you click on the link for the search engines you will be redirected to the AJAX version.
We have to think about this problem when we are designing web sites, not web applications. On real web applications the need of be search engine compatible is not as high as for news and product information web sites. Or will Google change their search engine?