I remember a few years back I was vacating a position as a contractor, and I was asked for recommendations. So, at the time my business was contracting, and I didn't really need as much help as I had. I recommended they hire one of the guys who was working for me but it was a "well, he can do the job, but here are what's wrong with him. I recommend you hire him"
The client didn't bite. later the body shop/recruiter who had gotten me the gig asked for recommendations, and I said the same thing. Apparently he talked the client into hiring my guy, and the client was pretty happy with the guy for a year or so. (the client hired me again when the guy left.)
Would it have been better for the client if I was good at sales and able to directly sell the guy? maybe.
(my other minor nit was that nobody gave me a kickback. Eh, I did get the guy to work for me at way below market wages for a year or two, so I got something out of it.)
But the upshot is when I give a recommendation, I see it as doing a favor to the company or person that has the open position more than a favor to the person I'm recommending. I mean, if I didn't think you were qualified, I wouldn't have recommended you for the gig, right? sometimes my recommendations are in the format "person X is perfect for the job, but you are unlikely to catch his interest"
On LinkedIn, though, it is different. the recommendations are setup as if you were doing a favor to the person you are recommending, which makes it much harder for me. I mean, how much of the negative stuff do you put in? hell, change the situation and a massive flaw becomes a massive advantage.