I also personally will only wear a tartan I have a blood connection to. However,(just to play "devil's advocate") how about where a clan ends up septs of various other clans? For example: my Muir blood is directly from a sept of Gordon. No problem there for me, (especially as two other families in my bloodline are also Gordon), but the Clan Muir fragmented & became septs of Gordon, Campbell, Stuart, & Donald. Does that increase a Muir's options or confuse the issue further?