Richard Best did a poll asking people a series of questions regarding redistribution of commercial themes and plugins. Since he did the work, I'd request you go to his site for the full poll results, but this paragraph alone is interesting enough for this post:
A majority of those who took the poll – 76 of the 121 people – think the practice of purchasing or otherwise obtaining a commercial theme or plugin and then either reselling it on a public website or giving it away on a public website, is unethical, regardless of whether it’s permissible under the GPL. A further 10 people don’t know whether it’s unethical but don’t like it. The remaining 35 didn’t have a problem with it if the GPL is complied with.
While the sentiment is totally understandable (and one I have too, often times), it's pretty amazing.
Check out Richard's post,yet another insightful contribution from his WP And Legal Stuff blog.