The blog linked below is from the guys at Sales for Life and details some research into why social selling can be a disaster. They talk about metrics and training and management buy in and other problems but I think the biggest reason social selling programs fail is actually something different.

Think about a group of single friends in the pub, there is always one who knows exactly what to say to engage strangers, a couple that are hit and miss, one who is an absolute walking disaster area but so thick skinned it doesn't matter and of course one who breaks out in a sweat if anyone of the opposite sex comes near.

Social selling is the same - it's clever and nuanced and not everyone can do it. You can provide the training, buy-in from the board and reinforcement but as they say, you can't polish a turd!  Some people are naturals at engaging with strangers on social, others can't and others just don't want to.