The 28% is apparently withholding imposed by the IRS, and to avoid it you have to fill out a form (I can't remember the number, but it's available on line through AIRBNB). The withholding should be available for return at the end of the year, unless you owe taxes. I consulted my tax accountant about this.
Different cities have imposed different tax structures on AIRBNB, and laws are rapidly changing - in Tucson we are now accountable for city lodging taxes, and the county is trying to re-classify AIRBNB property owners a commercial, thus raising our property taxes. Whenever there is an income, taxation forces will make sure they have a cut - I can't really blame the success of AIRBNB for this.