On OneStop we have always resisted forcing users to login. Since it's mostly a read only vehicle a login doesn't add much value, and people find it annoying.

On CEpedia (our mediawiki based wiki) we insist that people login if they are going to edit a page. We find that at some point most users do login.

We host our own search using the Ultraseek search engine. It started out as OneStop Search, and has been extended for our other properties, CEpedia, IC Create, and AIM - to name a few. Since we started with OneStop search, the assumption has always been we had no user information to work with.

We have recently extended CEpedia with a registry that is hosted elsewhere, and while doing so figured out how to pass login information back and forth. All of a sudden we can know who is using CEpedia search!

We can now start saving a user's queries, combine that with organizational info from our corporate LDAP database, and their profile info from the registry - and perhaps offer a much enhanced search experience. While using CEpedia I tend to search for the same pages over and over. As a first step, having a quick interface to my last few searches will be a big time saver.