I have created a VOISIN surname project at Family Tree DNA. If you wish to join, please request this of me here:email@example.com
So why create a table of Y-DNA results for a particular surname?
Imagine the FINNEY family with two clans, a northern one (say, originating in Massachusetts) and a southern one (say, Virginia). Further, let's say all the northern FINNEYs match each other and all the southern FINNEYs match each other. If the FINNEYs in the northern clan differ from the FINNEYs in the southern clan in only a few spots, one could conclude that the two FINNEY clans had a common ancestor within the previous several hundred years. On the other hand, if the two clans differed by MORE than a few markers, then clearly the two FINNEYs are NOT related to each other at all. But by creating these two separate tables of DNA results we have also created a DNA "profile" or a DNA "signature" for each FINNEY clan.
Doesn't sound like much but here's where the REAL power of this DNA "profile" or "signature" becomes evident:
1) suppose a FINNEY gets his DNA tested and has no documentation at all: we can now "place" him with one of the two clans and he will then have this line established when, before, he had nothing at all;
2) or suppose a FINNEY gets his DNA tested and then doesn't match either of the two clans: he obviously had an adoption (or an orphanage or an illegitimacy or merely a name change, etc) somewhere in his past FINNEY ancestry;
3) now suppose a FINNEY gets his DNA tested showing that he is a member of the NORTHERN clan but his documentation shows that he is a member of the SOUTHERN clan: this guy has an error in his underlying documentation; and finally . . .
4) let's suppose there were numerous inconsistencies in this underlying documentation. This is usually the result of "mis-associating" with the wrong FINNEY ancestor.
Last names were not adopted in Europe until AD 1300 to AD 1600 and while last names were brought forward correctly AFTER this period of time it means that this custom was not followed at all BEFORE this time and only sporadically DURING this time. This means that for some surnames (Flanagan, for example) that none of the Flanagans match any of the other Flanagans. That's an exaggeration but you get the idea.
I can be reached here if you prefer:firstname.lastname@example.org