I just wanted to add this in, to those that are ABUSING this privilege, please do not ...
I mail quite a bit of stuff, like in the neighborhood of 10-15 packages per day, via USPS Priority mail for my business ... these free supplies can almost be a small miracle for small businesses like myself ... for example the 12x12x6 box that they offer FREE costs $1.69 at OfficeMax for one ... if I ship 10 items at that size per week, that means I would normally be using $16.90 (+ 6% PA Sales Tax = $1.01) worth of my bottom line to purchase shipping supplies, this may not seem like much but over a year that equates out to like $878.80 (+ 6% PA Sales Tax = $52.73) ... again this is my part time business so losing nearly $1000 @ year would just "hurt" my bottom line and any extra income I bring into my family ...
My post office is very grateful for the amount of business, and amount of money I spend per year on Priority Mail shipments ... plus if and when I have extra supplies (such as the time they sent me 10 rolls of the priority mail tape) ... I took it back to my local P.O. and they were pleased because they will readily use it quicker than I would ... and I have been told by my local post master that because people ARE abusing the system and using the boxes for storage, moving, turning them inside out and shipping media mai/parcel post, using them for trash recepticles, etc., the USPS is considering switching to a FEE for these items when ordered in bulk and also when used at the post office ...
Just my $0.02 but probably worth less than that to those that are abusing the system ...