intertwingly

Patrick Chanezon: Google servers support gzip encoding, but only for certain HTTP User-Agents  [via Mark Baker]

I would be curious to know under what circumstances an application would send an Accept-Encoding: gzip, but not actually accept a gzip encoded response.

Generally such a header is intentional.

P.S.  No, I don’t think that this behavior is an outright bug.  One could argue that it is an unfortunate or unwise policy, but not that it is incorrect. However, for caches to operate correctly, the response SHOULD include a Vary: UserAgent header.