I was going to say the same thing as Rathdown; it's not really fair to claim an 8 to 1 ratio for the clan Gunn, when the name MacQueen itself means "son of Sven/Sweyn." Just because the person who happened to type out the Gunn sept list listed more variations of the name than the person compiling the MacQueen sept list doesn't mean much one way or the other.

Unlike Rathdown, however, all the Swans and Swansons I know seem to have joined up with Clan Gunn!

Despite what the Lord Lyon's web site says, it's really not that uncommon to find the same surname listed among more than one clan. The name Allen (which is my mother's maiden name) is listed among clans MacKay, MacFarlane, Grant, and MacDonald of Clanranald -- however my Allens are actually English! It just reflects the reality that there may be multiple origins for the same surname; that families moved around, and often changed clan allegiances as a result; and that historically what clan you belonged to had little to do with your surname anyway.

I hazard to say that most people who consider themselves part of "Clan X" don't really have 100% proof positive that they descend from that clan. They do the best they can with the information they have.