Taggle, search engine of the future, will not be a web-crawler
Brilliant idea: Taggle, an hypothetical search engine of the future, to search into folksonomies.
But Taggle will not work with a traditional webcrawler or robot behind, that's for sure. Del.icio.us has a strict robots.txt file forbidding access to robots...
However I do believe that Taggle will exist, based in web services, the APIs of providers, feed aggregation or other non-crawler method.