We've stopped using "ØMQ" in text and now just use "ZeroMQ" in most places (like in the Guide). The original choice was to annoy people into remembering the name... it kind of worked though got tiresome after a few years. I still like the logo.
The worst part is that now you're left with people who don't quite know how to call it. Just looking at the thread, you can see variations like ØMQ, 0MQ, ZMQ and finally ZeroMQ all in both upper and lowercase.
