This isn’t going to fall well on all ears… especially if you’ve already incorporated this into your wedding. Allow me to apologize in advance.
Do not ask your guests to write their requests on the back of their response card.
Do the math. If you have 200 guests and they each make a request, your DJ will have a list of 200 songs to play. Most of their requests will be a dance song, and only about 50 dance songs can be played in a 6 hour wedding. And you DEFINITELY DON’T WANT to get stuck with a list of 200 first dance songs! Talk about slowin’ down the night!
So rather than ‘honoring’ your guests by allowing them to take part of your big day, you’ve now completely ignored their wishes because your DJ would never have time to get to all of their requests. There’s nothing special in THAT.
Besides, your non-dancers are having influence over your playlist, too.
While the thought behind this idea is that guests will request only the songs that they will dance to, unfortunately, that isn’t always the case. We see it time and again at weddings. Guests walk up, anxiously request a song…and then run back to their seat to sit and enjoy it.
Alternative: If you really dig this idea, and can’t restrain yourself…put up a list of the top wedding hits on www.surveymonkey.com and create a poll. Allow your guests to rate their favorite DANCE SONGS, and ask your DJ to incorporate the top 10-20 rated songs into the night (depending on how long your reception is and how many requests of your own you’ll have). You can email the list to your attendees, and watch the results with delight! (But don’t allow write ins!)
You’ll find this list at http://www.discjockeys.com/top_200.php. (We have our own list on our client-exclusive site, and it looks a bit different. If you’re a client of ours, please check that out instead!)
This will allow your guests to ‘rate’ the songs they like from a list of already proven stuff, yet they won’t feel alienated when their ‘original thought’ wasn’t played on the night of your wedding. And believe me…they will be hounding the dj for ‘their song’. Even if their song is an awful request, they feel a sense of entitlement because they wrote it on that cute little response card and sent it by mail.
With all of this said, we do think it’s important to honor your guests in any way possible. Find out the first dance song for your grandparents, special aunts and uncles, etc., and ask your DJ to play it for a slow set or anniversary dance. But be careful of how many people you ask. If your party is thumpin’, you won’t want your DJ to slow it down TOO often. Try to restrict the list to those closest to you.
Good luck!
Diana 
Awesome ideas, thanks!