Originally Posted by chaoscript Like every site, You need to build the database. Cheers.

To match even 50% of given MD5 hashes, at an average rate of 1 million md5's added/hour, that would take over 1.94 x 10^28 years and consume much of the mass of the Earth in terms of storage required since at a guess you'd be looking at needing ~10^26 Terabytes of storage. Building a smaller rainbow table of commonly used strings would be way quicker and cheaper, but still would take a while and the site would then not live up to expectations.
Whilst I'm far from an expert on cryptography, I believe the ~best published MD5 collision algorithm can give a collision for a given hash in about a minute on a medium-powered laptop but even so this isn't the approach taken and is impractical without a dedicated server.