My latest column for The RESTful Web, httplib2: HTTP Persistence and Authentication, is up on XML.com.
In the article I cover HTTP compression, of which httplib2 supports both "compress" and "gzip". I remember reading that "deflate" was to be avoided but couldn't remember the reason. Walter Underwood wrote me to point out a post on google groups that explains the small set of compression algorithms that were interopable with browsers circa 2003. Remember that httplib2 is a client application and not a server so the types of compressions that work on browsers is irrelavant, but it is interesting to see issues that can arise.