This issue is related to using the DNA tests to help with your family tree research, specifically the cousin matching. I know that sounds obvious, but there seems to be a lot of focus in these forums on the ethnicity which I don't think really helps with that.
This may have been discussed before but I didn't see a specific thread for it, but for those of us who still have living ancestors, I think it might be best to test them first. The accuracy of the cousin matching decreases each generation back from you, and eventually becomes statistically meaningless (I think I read ancestry says at 5 or 6 generations). Because of that, and because most of us have limited resources, it seems like the most bang for the buck would be to test any living ancestors before you test yourself, and the more generations back the better. For example, an ancestor who is my ggggg-grandfather might be too far away from me for any matches to show up, but that same person would be my grandmother's ggg-grandfather which is closer and more likely to have matches. This of course only applies to that specific branch of your tree, but once that person dies then that information will be lost forever. In fact, you could argue that if your grandparents are no longer living but still have living siblings (great aunts/uncles), testing them would be of equal value since their parents are still your g-grandparents. For those of you young enough to have all 4 grandparents, if you are willing to spend the money and they are willing to take the test, that gives you a 2 generation jump up your family tree as opposed to testing yourself. There won't be anything in your DNA that isn’t in the DNA of those 4 people, but there will be things in their DNA that aren't in yours.
In my case, both my parents are alive and I'm getting both tested at my expense, and each has a sibling and I'm considering testing them as well since the siblings could have some matches that my parents don't.
Any thoughts? And no, I don't work for ancestry who would love to get every member of your family tested! They ought to consider a volume discount though . . .