2. I use RP data, and it lets me see the ownership, weather is single person, husband and wife, or whatever.. This helps in the sense you know your most likely dealing with 1 vendor
3. Rp data also shows when they bought it, and how much they bought it for. Obviously this is great info to have. If you know they bought it 3 years ago for 500k and now they are only asking 550k or less, most likely the sale is by a distressed seller for some reason (if you can find out that reason by putting 2 and 2 together from all your analysis then even better).
4.I have found a lot of REA's are really not that bright
This is part called effective preparation - you should have an idea of the circumstances of the vendor, knowing that you are dealing with the decision maker (pointless negotiating with anyone else - this applies to every negotiation). Some agents like to give the impression that they aren't that bright - many run a business quite effectively and are quite canny.
Also, agents can access information to find out what properties you own, its not hard. Not that they would be bothered I guess, but something to consider. Not all agents are fools, the best ones to deal with are the lazy ones that are out of area who under value properties and work for the buyer not the seller.
A decent agent will qualify you as a buyer ie. will establish your motives, your financial position, how much you can spend, when you will have funding available/how much etc. Out of area agents may appear to underprice properties however (quite strategically) they will present the property below market to ensure a quicker sale (and less time tied up for them in concluding a sale).
I've pretended to be a buyers advocate trying to secure a deal win win for everyone, when I'm actually the buyer looking for an outright victory.
REAs also lie. Some make up lies about having offers.
Acting as the BA can be effective, especially on the initial queries to sift through the BS is something I've done in the past, sometimes it has even been legit.
I've never heard that an agent may lie, just like they've never taken a dummy bid at auction.