[curtis]

One problem is that there's no easy way to build a regular expression index for the web. In the general case the only way to do regex search is to scan the entire content.

It might be practical to do a hybrid search -- a conventional word or phrased based search to return a limited set of documents that can then be brute-force searched using a regular expression. This could be especially handy for programmers searching for code samples, a position I often find myself in.

[seiji]

Regex capable code search: http://google.com/codesearch

[curtis]

True, but codesearch only searches codebases. But suppose I want to search for mixed content and code. A lot of my programming related searches lead me to StackOverflow, a mailing list entry, or a blog post.

[crasshopper]

You can't search for symbols though.