We didn't do pinnings at UCF. Instead we did lavalierings. The only thing I disliked about the tradition was that the fraternity would then razz the member who'd lavaliered his girlfriend and throw him in the lake naked or something. It was almost expected.
We also called lavaliering the "kiss of death" because once a couple was lavaliered, they rarely made it and broke up a few months later. The other lucky ones stayed happily in love, and some led to engagement, etc.
So, I think it just depends on the couple if pinning is a good idea. It think it can be a very sweet way for a fraternity man to show his love for his girlfriend.
... Of course, I'm convinced most girls are just in it for the sorority candle lighting they will get to celebrate the pinning.
