I got married two months ago and we did not put the registry info in the invitation. My DH wanted to, but I put my foot down because it is TACKY! People asked and it was no big deal. We got 75% of the items on our registries (Macy's and Bed Bath and Beyond) and cash. We only got 3-4 non-registry/ cash gifts and all were sentimental. So, people will ask and buy off the registry if they want to!
A funny story though- we were total B List guests at a wedding this fall for the sister of DH's friend. We got the invite like 5 days before the due date. But, we went and got a gift off the registry- which the card was in the invite. The couple was 22 and just out of college and their parents home. They had NOTHING. They registered for the most random stuff at BBB and Target e.g. a Wii, fondue set, creme brulee torch etc etc. And that's what all their 22 year old friends were buying them! The best was between the 2 registries, they were registered for 7 toaster/toaster ovens! We got them a variety of kitchen utensils (spatulas, spoons, pizza cutter, etc.) Not really exciting- but that's the stuff you use!
So, flash forward to our wedding. The totally regifted us! We suspected it because the gift was random. It came in a wedding bag that broke because it had been used. Upon inspection, there were a couple little pieces of wrapping paper still taped to it!
If they would have wrapped it, we never would have known. Guess what it was...... a toaster oven!
We were able to exchange it at BBB and got a $70 credit for it so alls well that ends well.