Unlike search engines, metacrawlers don't crawl the web themselves to build listings.
Instead, they allow searches to be sent to several search engines all at once.
The results are then blended together onto one page. However, problems still outweigh
their benefits. All have significant limitations as a comprehensive search tool.
Subject to time outs, when search processing takes too long.
Since most only retrieve the top 10-50 hits from each search engine, the
total number of hits retrieved may be considerably less than found by doing a
direct search on one of the search engines.
Advanced search features on individual search engines are not usually available.
Phrase and Boolean searching may not be properly processed or available.
