Well, I dont.
But, I keep my business small. I ususally dont do much advertising and for the most part I stick around a few specific subdivisions, doing on average about 3-5 clients per week. If youre doing somthing similar to this, I wouldnt worry about it.
If you are starting more than a part time, hobby type job, than you better tell the IRS.
:xyxthumbs Just my 2 cents.