Hey Apple,
I get that your first inclination might have been to be defensive. I've been in places on the internet where I've asked something of a group of people and I've gotten slammed for it. It feels suck. I get that. I also get the "if you're going to bite me, I'm going to bite you back" reaction, but the one thing a lot of the new posters here keep forgetting -- for some odd reason -- is that we're actually _trying_ to help you. You might not think we are, and you might think you've been given the green light because someone else has told you it's okay, but it's better to be cautious, especially with a new group of people, instead of burning the bridge.
I'm a huge bridge burner, so like I said, I know the impetus to react that way, but you're not going to end up finding the help you want.
What I suggest, since you seem pretty comfortable with asking MSCs direct questions like, "What companies do you shop?"-- I'd suggest trying to sign up with many of the companies that are "recommended" from the Official List of Mystery Shopping Companies (see the bottom right of this page). When you've registered, feel free to contact them to ask them that question. I don't really know how they'll react, _personally_ I wouldn't do it, but it sounds like you're pretty fearless in the face of such things.
The only other thing I really wanted to say was that-- in your original note, you'd mentioned that you would "trade" information, that maybe you could help other shoppers if they were willing to help you. In this place, we're a community. To establish yourself and to, well, I'd say "endear" yourself to the group, instead of fishing for something for yourself, maybe you could try hanging around on the forum for a few weeks and offering your expertise. Answer some questions, offer some advice.
I can point to every single person in this thread who has responded to you and say that every one of them has spent hundreds, if not thousands, of hours supporting other people on the forum (it depends on how long they've been here, in truth, some have been here for a very long time). I can say that every one of them helps without the mindset that they'll be getting something back for themselves.
Just food for thought.
Sending the best,
Jen