I occasionally get requests to connect on LinkedIn from complete strangers. They include no messages indicating why they want to connect to me. Some of them appear to be indiscriminate spam generated by people somehow pestering vast swathes of people to connect with them, while others make me think that the sender actually sent me them for some reason [i.e., I just got one from someone who worked in my current city in 2011-2012], but I’ll be damned if I can figure it out.
Why do people do this? It’s like walking up to someone on the street and saying, "Let’s exchange business cards!" Why? Who are you? Why should I trust you?