Im trying to get my sister to play a bolywood vs SE-asian pop set. She's got some interesting choons!

In addition to what Kate said;
Rougie - all you need is a set of headphones! If you have an Ipod then you have headphones! and some CDs! The reason why I would like people to DJ is it encourages them to be selective with their choices - if you stick an mp3 player on shuffle, well you wont be being very selective - and thus we will probly end up listening to loads of tracks that arent even YOUR favourites. Its the nature of mp-freeness that people tend to collect reams and reams of rubbish music - that they wouldnt pay money for in a fit!

Also - if you'd rather be out playing in the field, then you should be doing that!

to Dj you have to really WANT to play your choons to people - and you give up dancefloor time for that. Plenty of times during sets I've played I've wanted to be out on the dancefloor listening to my favourite tunes, but playing them to other people took precendence!

One more thing - mp3s can be really really dodgy sound quality - and vary a lot depending on how much the person that encoded them cared about the music ie it takes much more care and more time to encode them at higher bitrate and variable bitrate than it does to just whack a whole abba album on the net encoded at 128 (which is noticeably lower quality than cd).
As you can see, there are a lot of reasons why we dont want just 'radio playing in the background'. In fact, if it were that kind of party, then...well, it would be being put on by people who dont really care about music (ie not Kate, me, Biggins, marty, serena or anyone else that has taken a major role in making CG happen in the past).
I dont think its too much to ask that if you want to play your music at 150 people you should at least be there making sure its the best tunes you have.
Perhaps you were thinking about wiping your iPod and only putting Mp3s on it for your set? well that would in theory be ok - but wouldnt address the issues that Kate raised, and also - I think its likely that if we open it up to the ipod shufflers we will be listening to music that simply isnt good (or even sufficiently cheesy) in any way, cuz every man and his dog has an mp3 player filled with some good tracks, and many they may not have heard, or even like.