While I understand the reasons behind the wish, there are some guests (call me old fashioned) that like to buy presents because they've chosen a special gift for the couple.
I'm always happy to do it if that's what people want (like last Saturday), but there's nothing nicer, years after your wedding to get out something beautiful you recieved as a wedding present and reminisce...you know..to forever remind you of that day and that people who love you were there to help celebrate.
Just a thought.