For people who are members of several lists, this is a freightening possibility. For others, it is just extremely annoying. In the particular case in question the spamming was an unsolicited advertisement, but that's just the tip of the iceberg. People simply seem unable to withstand the urge to join the fun. And often it really is fun.
Readers take the opportunity to joke around.
This weak attempt at humor only took 72 seconds. Won't happen again. Complaints about spam use bandwidth, too. All the spam complaints have eaten up far more bandwidth than the original spam itself. Lets agree, no spamming and no griping about spamming.