Kind of a spin-off of reciprocal Facebook "liking", now there's a feature on LinkedIn where people can endorse you for various skills that you list on your profile.
I have not done a single endorsement. I generally don't use the features of the site, just like I don't use FB features very often either - I'm maintaining a presence without active participation. But I've received a number of endorsements. I don't have a sense of whether anyone puts value on these endorsements, if they don't then it's no big deal. But if they do...
I know I'm not obligated to endorse anyone if I don't feel they merit it, but what about cases where I know the people have these skills: Is it rude not to reciprocate? Or is it fine to continue to not participate?
(Someone I asked at work likened it to posting "Happy birthday" on someone's wall - it's nice to do, but if you start, you can't stop, and then you have to be really vigilant or someone may get left out and hurt feelings might follow).