I have no quarrel with a seller no posting to a PO Box per say what really get up my nose is that it is not until; you get to Paypal the seller advises they don't send to Po Box's.

Why don't they be up front and include that they don't post to PO Box's in the postal information. 

I did write to eBay support and suggested that if a seller did not post to a PO Box it be mandatory to include that in the postal information.  Despite all the rhetoric by eBay to me it will probably never happen