One of the problems with wearing t-shirts that have esoteric computer geek things on them is that periodically airhead girls will come up to you and tell you they like your shirt, and you’ll spend the next five minutes explaining that they have no idea what it means, and whatever they thought was funny about it is wrong.
Case in point, I was at a strip club the other night, and the girl sitting on the stage in front of me said she liked my shirt. I hadn’t dressed up to go there, so I was wearing the SYN/ACK t-shirt I had been wearing all day. It says “SYN” on the front, which she could see, and “ACK” on the back, which was covered by my jacket. Those of you who know a lot about TCP/IP will get it, but even then it isn’t really that funny. I was already fairly certain I knew the answer, but I asked her if she was a network engineer. “No,” she explained, “I like it because it says ‘sin’, only it’s spelled with a ‘Y’.”
The PUA crowd will tell you that girls just use your shirt as a lame excuse to come talk to you. Indeed, there are worse things than having to explain your shirt to a naked chick who has her heels on your shoulders. However, it is generally not a good idea to start a conversation with a girl by explaining that she is not smart enough to understand your shirt. Even if you believe in the neg, establishing yourself as intellectually superior will probably still work out to you being socially inferior.