[_ck_]

I guess it would be a good alternative to akismet (or even in addition to).

Your code can be cleaned up and condensed considerably.

It also could benefit from some security checks on the $_POST data being injected into the url.

Here is an untested, condensed version with some mild security checks on the $_POST

http://pastebin.com/f7a50d82a

(there is also an alternative to curl in there for the 50% that don’t have it on their server)

I took out some of the extended manipulation of the returned data that you didn’t need.