But seriously, I am sure you have heard that some witches do practise naked. Yes, some do, I believe it is primarily a wiccan thing. The idea behind it is that you eliminate all boundaries between yourself and the Gods and let them see you in your most natural state. Working naked is also adopted because it means you are not bringing dirt and pollutants on your clothes into the circle.
I suppose in a sense I do adopt a similar belief, when I do formal ritual work I always bathe beforehand, wash my hair and scrub my face. And I'm very much doing that because it is important to me not to hide behind fancy clothes, make up and artifice when working with my deities.
I think it is important to feel comfortable with how you dress when you work magic as feeling self conscious can have a negative affect on the work you do. So wear whatever feels best for you.
Image http://www.sxc.hu/photo/1340313 (african fi)