I agree with this, about 98%. In the past few weeks I have received connection requests from a number of people, some of whom were 2nd degree connections, some of whom were members of groups I was in, and some of whom were complete strangers. In the case of 2nd degree connections (friends of friends), I always accepted. Any friend of a friend of mine is a friend of mine, right?
If the request came from a fellow group member, again I would be inclined to accept, but I'd usually check out their profile first. Mostly just to make sure they didn't have "serial killer" listed among their hobbies.
It's the last case that gives me pause. As I said, LinkedIn is about connections. If I turn down connections from people I don't already connect with in some way, I lose. My network grows more slowly, which means I miss out on potential job leads. But if I connect with everyone, I open myself up to some things I'd rather not.
What I do, in cases like that, is troll their profile. I'll check out their group activity. Maybe see if we have any 3rd degree (or more) connections. I'll try to figure out how they came across me as someone they wanted to connect with. I received a connect request from someone two weeks ago who picked me simply because he was graduating from high school in the same town as I had. I honestly think he just typed the name of the town in the search bar and hit "connect" and when it asked how he knew me, he selected "went to school together." I wrote a nice (I think) note explaining that while I was flattered that he wanted to connect, I wasn't sure I had much to offer a brand new high school graduate, currently in a different part of the country, who had no experiences in common with me.
But usually I'll accept the request, because I figure it was made for one of two reasons: 1) This person has something they want to offer me (job lead, connection, advice), or 2) This person thinks I can help them with something. Well, shoot, I'd be dumb to turn down the first, and if someone thinks enough of me to ask for help, I'm probably going to help them.
What about you? Are you super-selective with your LinkedIn connections? Do you automatically accept everyone who asks? Or are you somewhere in between?