Actually a whole lot of research. Indeed, one would have had to read through about 10 pages of rules and even then one could have missed it. Perhaps this is standard practice in the UK, but airlines in the states have these programs and still give miles. Very disheartening practice. Indeed, it's a horrible "bargain". AND, it will cost Virgin more than it saves as I have warned off several other colleagues who were going to try Virgin instead of BA or UAL.
I don't think any airline in USA has anything different. Delta allows you to pay for some part of your ticket with miles and it very clearly tells you that you will not earn miles for that ticket. So, theorotically, if you decided to pay 10$ out of a 1000$ flight with your miles, you will end up with 0 miles.