We had a similar experience when staying at the Polynesian in August '03. We followed three teen-age girls onto the monorail, they were dripping wet, wrapped in towels. Overheard one say to the other..."That pool is hot!!! Much better than ours at Sports!" No way were they DVC members. In order to pool hop as a DVC member you must be staying on points. I don't think you'll find too many DVC'ers using points at an AllStar resort.
Also overheard on a different day..as I sat on my way in the back chair, since all the chaises were taken.....a woman say to her dh, "Honey, this might be a good place to stay if we could get a really cheap rate. But I don't think they are going to beat the rate we got at Holiday Inn. We're better off just using the pool." Then she took her drink to her pool-side chaise!!! Now, that bothers me a lot!!!
I still think they should do every hour pool checks for ID's. A pain yes, but it might discourage some of the pool-hopping by those who shouldn't be doing it. As far as the DVC people hopping, I think that you will find that most don't take the time and effort to hop. Of course some do, but for the most part it's a non-issue.