You're right that it's a publicity stunt. But is that a bad thing?

Yes, if their goal is to make their website popular in the longterm and a hot destination on the web. But what if their goal is just to garner some publicity? This did that.

Also, publicity stunt implies a lack of substance, but I think the near complete outsourcing of their site and image management really is an interesting event. (And probably other people do too, so in the next couple weeks people will write blog posts about whether this is a turning point on the web or whatever – and each one of these posts will mention Skittles. A few months from now there might be a newspaper or magazine article about it, which would reach a different set of people.)

So it is a gimmick, but a genuinely interesting one that didn't cost much and will probably sell a few more bags of Skittles.