The only costume I didn't take was the one cabaret belt that I owned at the time. Not that it's worth a lot of money, but I'm really rather fond of it and I didn't want to take a change with it getting all dusty and me not being able to figure out how to clean it. Not to mention I don't know what I'd do if one of the bead fringes broke out there and left little tiny beads everywhere...
I didn't have a problem with anything else I took. Some things you just wash as usual when you get back (cholis, skirts, pants, etc.). My black tribal skirt was solid grey with dust when I brought it back, but I just threw it in the gentle cycle and it was fine. Some of my tassel belts I smoked out to clean them. I haven't had any problem with the tassels nor have I heard about anyone who has.
I personally don't assign a lot of value to most of my stuff, so if something happened to it, I'd be sad but not devastated. I know other people are differnt, that's why I give the disclaimer about if it's worth that much to you, leave it at home. To me, I'd rather get use out of it than have it sit in my closet and be afraid to wear it anywhere. :)
Some people make stuff specifically for BM, it's really a personal thing. It's a good excuse to make something new. In fact, the very first belly dance costume I ever made was specifcally for BM. :)

Last year I took an older skirt that i had and all of my harem pants.. I also took an older tribal bra and belt set that I have but did not take my hard to clean newer set. I also took most of my jewelery.. and all of my turbans. Your tassels should be fine, unless: it rains and mud splashes up, or they are too long and they drag in the wet mud.. For the most part anything that can get wet you can get playa out of with enough washings.. Playa can be hard on metal.. My head piece from last necklace from last year never did recover.. but that is okay it hurts me anyway. I would not wear anyskirts that have felt or material on the the trim that dust will be hard to get out of..

This year we will be doing a costume exchange so if you have some old stuff that you want to donate please do so.

Hair for me is difficult to deal with (mine is long)... The first year I just dealt with it being a pain.. I tried to keep in braids for most of the week, or under my hat... but a min out of the shower and it is gooey from playa dust and wetness..Lots of conditioner... and then braid it as soon as possible and leave it be.

This past year I had fake hair in many different color put in before I left for the playa. This year I am going to try and wrap it in different colored fabric which I think will help protect it... and then it wont be such a pain to take and and deal with after the playa.. Last year it took me about 1 day and a half to get all of the fake hair out of mine, get it washed, conditioned and get all the tangles out of it..

If you have hair that is fine and long like mine you dont want to leave it up to the wind and dust unless you want permanante dreds.

Kat