I was without Net access for last couple of days, in which a mild storm has built up around the issue of sponsored themes in the WordPress community. It all probably started with Mark Ghosh banning them from Weblog Tools Collection, and then Matt excluding them from the official themes repository.
I cannot say for others, but I am glad that the sponsored themes are not being encouraged. Here are some thoughts:
Link Because of Value, not Money
Sponsored themes would include link for an entity who paid in money, and the community which uses that theme would end up promoting the company, whether they like it or not. Of course there are links to the theme author who has worked on it, and WordPress which is being used for the blog. But this is because they provide value, not money. Also, I feel that these links provide as contact points for the reader to know which tool is being used and who should get credit for the theme, just like they know who to give credit for the content.
Sponsored Themes are not the same as Advertising
I do not think sponsored themes are same as advertising. One is because the web site owner chooses whether to put advertising or not, which advertising, where and when to put it. Also, the web site owner can do this only for his/her web site not others’ in the community.
Sponsored Themes are Unethical
The basic reason I feel strongly about is because this is forcing the community to promote vested interests of a company, especially without any control over it. This is manipulating the community only to get a better search rank. This will always have side effects, like people ripping off others’ themes so that they could build a sponsored one. The focus moves away from contribution to the community and towards earning money. And this is why think Matt’s decision is good.
I do not mean to say that earning money is evil. It is important, but it should also be straight forward. I think asking for donations or even selling is better than sponsored themes. Or the users can unknowingly end up being party to promoting a company without their knowledge.
As I mentioned earlier, I can only talk for myself and can be quite subjective. However, I do avoid sponsored themes because I think they are arm-twisting me. And I am glad that they are being discouraged.

July 16th, 2007 at 5:35 am
I have the same though on this matter and decision to discourage them is well acceptable to the WordPress community. Themes are sponsored with the sole intention of buying bunch of link backs and it doesn’t have the motivation to support the Theme author or to help the community by keeping the Theme free to use.
July 16th, 2007 at 8:05 am
Sponsored themes are often illegal. To prevent people from taking out the links, they’re licensed under proprietary conditions. That’s illegal under the GPL under which WordPress is released.
July 17th, 2007 at 11:47 am
Yes Benedict, and the motivation is what will matter in community contributions. And a money motivation is not bad, but it should be explicit, not implied.
Good point Alejandro. But I am not sure if GPLv2 says that, GPLv3 might target that.