He's notorious for it. He usually keeps his front hand stretched out with his fingers straight pawing at your face. Ostensibly it looks like he is just judging the distance or possible throwing a fake jab but an "accidental" side effect is that he constantly sticks his fingers in his opponents eye. Hendrix specifically talked about how worried he was about it before the fight and his counter appeared to blocking Koschecks claws with his own hand. Also, I think he made a big deal out of being poked the first time so that if it happened again Koscheck would lose points.
In summary, I have the nagging feeling that people think that GSP is just going to take this fight to the ground and GnP Thaigo to victory. However, with his past game plans calling for initial standup and clinch work, I think Thiago has a great chance to neutralize GSP’s wrestling with his leg kicks. After a few of those land, GSP will be unable to take Thiago down. After that, Thiago will be able to stalk GSP down and let his hands and feet really fly. If GSP is able to take him down, Thiago should be able to tie his up and get the ref to stand them back up.