Who is entitled to wear a tartan?

There has been a little debate going on recently at the X Marks the Scot forum about who does and does not have the "right" to wear a tartan. I've been a contributor to this discussion. Some enlightening opinions have been brought forth. Well worth a read!
http://www.xmarksthescot.com/forum/showthread.php?t=11737&page=1&pp=10