not2easy - 12:34 am on Jul 18, 2013 (gmt 0)
I have been using my local Post Office's street address as an address for nearly 10 years - with their blessing. I have a PO Box address which many will not ship to, but even UPS will deliver to their street address and they pass it along to me.
Edited to add: to open a PO Box account these days, whether business or individual - you must provide proof of who you are, it could be that a receipt for domain purchase would be acceptable. I do not know what documentation is required but I do know you can't just fill out a form and open an account.