pipeline_prefetch woes

[rihad <rihad@xxxxxxx>]

There's at least one site that doesn't play well with the (presumably) 
pipeline_prefetch setting:

http://www.imdb.com/title/tt0091635/
gives:
404 - Sorry, no prefetching

This effectively makes pipeline_prefetch unusable as a common strategy.
Why would they want to do that? Any negative impacts of HTTP pipelining 
on the servers?