- You can get results from multiple search engines without having to visit each one. It gives your search a broader scope to look at, since each search engine's index differs from each others.
- May need to decode query forms.
- Translations of query syntax and fields not exact.
- Some sources don't sort by relevance.
- No way to compare relevance.
- Vulnerable to search spam.
- Results returned as HTML without useful tagging, require screen scrapping.
- Variable quality of search engines.
- Must keep up with changes in source engines.