I also don't social network for work. Can't be bothered with twitter and I only use Facebook for my own social purposes. It would not occur to me to use such a site for work since it would so easily compromise my anonymity.
The best place to learn about the work we do is to go out there and do the work, build up experience. I find that forums such as this one are also very helpful. There are job postings and experienced shoppers here who are willing to share some of their hard-earned knowledge. Books, DVDs, etc. are marketing tools and I would not find them helpful.
From a shopper's perspective, if MSCs are looking for shopper loyalty, they need to pay on time, each and every time. That's the main one! Other than that, honesty and transparency in shop instructions, fair wages, open channels of communication whether that be by phone or email, editors who are fair and don't act like they're editing the next great American novel, etc...
As to where to find us amazing shoppers...the MSCs need to let us know when they have jobs available. The best way to do that is either to email their shopper base (keeping in mind geographical logistics ~ I don't care to hear about the jobs available in Alberta when I live in Quebec) or to advertise job opening on forums such as this one. We're a crafty independent bunch and we're used to having to troll for work.
Does that help at all? We're not a bunch of meanies but we are wary when we feel people are trying to get something out of us for nothing.