The two definitions, though different, actually have quite a bit in common. If the practice of surreptitiously acquiring the e-mail addresses of special interest group list members is tolerated, then conceivably, you may be faced with the problem of your electronic mailbox being innundated with announcements and solicitations of all kinds topics and products. 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.