I believed when I noticed this being started that a greater fraction of left-handed than right-handed people seeing this thread would bother to add their self as a statistic.
Although I didn't vote myself, and I am right-handed, or ambidextrous, my reasons were unrelated to my belief, which is: most left-handed people will assume, when reading this, that knowledge of their existence is desired, and so will vote as a left-handed or ambidextrous person. Right-handed people will assume their existence is assumed, and that it is assumed to be at a certain ratio to left-handed people already, so would not be as likely to vote. (They'd feel their input to be less significant)
Since it's a forum and people will choose where to respond to whom, the results you get are tainted with prejudice.
Also, if your hypothesis is that fans of The Dresden Dolls are more creative, and thus are likely to contain more left-handed people per person than a random sample, you should also consider that not every fan uses this forum, and the type of people who use The Shadowbox, as opposed to listen to The Dresden Dolls, might even be more relevant than the fact that we all share a taste for their music.
Everyone is potentially creative. Creativity seems that it would be a difficult attribute, or potential, to quantify.
I wonder how it was originally determined that left-handed people possess more creativity.