Spam isn't just about e-mail anymore!
Spam used to be the problem of e-mail. It was the unsolicited and unwanted commercial messages from people you didn't know and with whom you had never had a business relationship. Now the concept of spam has expanded to include social media and can also include someone messaging you out of the blue with the only desire to send you a link to a website.
No one likes to receive spam, whatever its source or purpose. People who send it earn a bad reputation. The idea behind the social media is to make connections with people you know or through people you know. Commercial messages are deemed all right if they are given in the context of receiving some other information or some other benefit, but seen as unseemly if given solely to sell them something. In many social media, sending them is a quick ticket to being unfriended or unfollowed.