In a recent post, Hervey Wilson explains how the WSE 2.0 team is enabling side-by-side execution of WSE 1.0 and WSE 2.0. One fallout is that the WSE 2.0 assembly is now Microsoft.Web.Services2. Importantly, the namespace is changed as well. Hello global-search-and-replace. If Microsoft plans to do this kind of thing often they should add a namespace rename refactoring feature to thier Whidbey VS.NET product.
Even if your not interested in WSE 2.0, this is a good primer on how to enable side-by-side execution in your own libraries. It would be nice if Microsoft could work up some guidelines on making libraries side-by-side ready.