Sites like hollywoodgrind.com get too much traffic for Apache to handle. I setup a reverse proxy/HTTP server acceleration squid cache server (http://www.squid-cache.org) only to discover that WordPress does not send the correct header information for pages to be properly cached. I already use wp-cache 2.1, but it cannot assist Apache in scaling to the 800-1000 transactions per second that the squid cache server can provide. For sites like mine it would be a huge cost savings to be able use the squid cache server as the front end and wordpress + apache on the back end.
I like wordpress, and would like to continue using it, but it will not scale to large volumes of traffic. Movable Type has corrected their header info so MT can be used with squid cache.
Fixing the header problem so that wordpress can be used with squid cache server should be a priority with so many large sites now using wordpress. Why hasn't this header issue been fixed yet? Is time and money the issue? I hope the wordpress team fixes this problem before I run out of options, and have to switch to movable type.