Always an interesting topic, couple of quick points:
1) RE: Selling on eBay versus scalping. I think the key thing here is the initial listing price. If you list the figure for more or less what it cost you, and let the bidding determine the value that's just free market economics, not gouging. If you were to list something for double or triple what it cost you, plus shipping etc, then that is sort of crossing the line into scalper territory IMO. For mail-away stuff it can be hard to determine what the initial value should be though, given the UPC aspect. So I think there can be some leeway there.
2) The only possible criticism I could see with some validity is that the mail-aways are limited edition items with a finite production run, so in theory buying them up in bulk could reduce the likelihood of an individual from sending in and getting their form redeemed. Not really sure where I come out on that.
3) I think it's the height of hypocrisy for any site, not singling anyone out honestly, to complain about "scalping" whatsoever when they have sponsors like Brian's Toys and other Dbag sites that were selling the SDCC sets for jacked up prices and things like that. Those guys are WAY worse than any individual scalpers roaming around out there, IMO. They have taken it to a whole new level. Just because they pay for advertising does not absolve them of the moral implications of what they are doing. They're scalping, plain and simple.
I don't have a problem with this stuff for the most part, there can be a good deal of grey area involved.