I have yet to send a reception report to any AM radio stations. Although, I have done so via snail mail a few times for shortwave broadcasts through the years. However, I did request a KAAY bumpersticker from the station's website recently as last I checked they will send them to Arkansans without a fee.
There is no doubt that cutbacks and changing technology are both affecting QSL card returns for reception reports. Many shortwave broadcasters, including pirates, have switched to sending electronic QSL's via email. As of last month Radio Sweden discontinued mailing printed cards and is only making schedules available online ( http://www.sr.se/cgi-bin/International/nyhetssidor/artikel.asp?nyheter=1&ProgramID=2054&Artikel=3133057 ).
Radio Taiwan Internantional has also discontinued sending printed copies of Taiwan Journal and it has been replaced by Taiwan Today online. As far as I know they still send cards and are a very easy catch for beginners due to broadcasts relayed out of Florida.
Sending postage and a self addressed stamped envelope is probably a good idea as I'm sure you know the financial situation for many AM broadcasters looks bleak at present. While I am not a member of the National Radio Club, they do offer a variety of pre-written forms available for download to any listeners who might be considering sending AM reception reports or requesting QSL cards at http://www.nrcdxas.org/. It only seems fair that when writing to stations you provide them some information that might be helpful or useful to them and the club's forms include a nicely laid out way to grade the quality of what you might have heard.
Now might actually be a good time to try some AM dxing and station commuunication, I suppose it is better late than never. I sincerely hope that many of the AM stations that have not already succumbed to entropy manage to survive. Late nights just wouldn't be the same without them, no matter what new technology brings.
I agree...now is the time of year when atmospheric noise is falling in intensity and stations will sound clearer for it. Dave M. had some good notes in a post awhile back about why stations seem to sound clearer. Wintertime is a good time for us Hams to operate the lower bands, as well, since this noise lessens during the season. Shortwave listeners also enjoy more noise-free listening, too!
Some of the worst noise levels are in fall and in spring, when the rains come. Here on the Gulf Coast, some thunderstorm crashes literally rip your ears off, even without headphones! I can see how a spark gap transmitter can be heard hundreds, even thousands of miles away! Thankfully, we no longer use them (they're outlawed) and we can enjoy the teeny-tiny bandwidth of a CW (Morse Code) character or the wider bandwidth of voice and music via AM, FM and single-sideband with ease.
Thank you for the sources you mentioned!
Bud S. (firstname.lastname@example.org)