Launched Stack Exchange sites display ads picked by the community. On Stack Overflow, these ads are specifically for open source projects. On SU, SF and Stack Exchange 2.0 sites, there is no particular constraint; the suggestions include “anything else your community would genuinely be interested in”.
Besides offensive or “NSFW” content, are there any constraints as to what may be suitable for a community ad? Are commercial ventures ok? Does the ad have to be at least somewhat related to the site's topic?
Are there rules that moderators should enforce, or is it entirely up to the community?
Note that Stack Overflow is out of scope for this question. Also, beta sides don't get community ads. Only SU, SF and launched SE 2.0 sites are concerned.