I use it.
You can get pings based on other information that are out there on the net.
It is an aggregator site where your busyness and professional connections can be posted. You can post a resume and a profile if you desire. Other folks who know you or have worked with you can ask to be connected to you (though as you point out sometimes it picks folks who maybe 3 or 4 degrees away).
It is not a bad site. If you don’t want to use it just delete the request from you email.
Do you have any idea why my replies to people asking questions of me are never received or acknowledged, especially when they are soliciting sales?