From the docs for tagged paremeter:
List of tags delimited by semi-colons of which at least one must be on a question

Yet, when I execute this query (http://api.stackoverflow.com/1.0/search?tagged=java;algorithm&sort=creation&min=1296897084&pagesize=2), it returns a single 8-hours old question, tagged both algorithm and java. Naturally, since that time lot's of newer questions has been posted in both algorithm and java tags separately.

It looks like, current interpretation of this parameter is every one must be on a question instead.