Hi Margaret,
Thanks for the info you posted first, and to everyone for all the interesting discussion. Ancestry is like great big blundering dinosaur - you can't ignore it for it is the biggest kid on the block, but it can be so frustrating and unhelpful. I have become so discouraged with the difficulty of finding useful matches among my 25,000 that I have hardly checked it out lately, so your note about the map was helpful thanks. I, like others here, wish for a chromosome browser and (surely this wouldn't be difficult!) a simple search for match names, but I guess the map is better than nothing.
Like others here, I had only a few of my matches showing on the map, mostly 4th cousins it seems from the ones I checked. Presumably this is because it is only a beta version. But the good news is that I did find someone else who lives in Australia that I hadn't noticed before (I don't regularly look through 500 pages of matches checking out each one!!!) and he had a common match with two people with a surname I am interested in, so that was breakthrough that I might never have come across without the map.
So let's hope Ancestry turns the beta into a full working product that allows as to filter what the map shows, and that they continue to develop other useful tools.