Personally I use a lot of forums, and do advertise also.

But I think maybe we should have stronger rules.

Such as, make at least 5-10 posts per month or week, before you can post another add.

It just annoys me when people just spam and use the forums for that purpose, rather than taking part and giving back on what they are taking.

My 2 cents.

Sounds reasonable to me.

IMO this has its pros and cons. It may increase the activeness of the forum but more spam/irrelevant posts will probably pop up and keep the moderators busy instead...

Well true, but it is annoying that users just post it.

It is pissing me off, I come on for new threads and sigh it's just adverts, adverts, nothing great.
We need some proper banter, not loads of adverts
Besides, it's a community not a advertising forum, and that's what 60% of people do! They need to pay in some form, such as taking part.

I try to keep it to 1 a month but I always take part in the forums I use, it is a good idea also, because you can put your sig in and so on.
Then your posts have use.

But I understand you might get spammers

If the limit is low enough, I think it's a good idea. But I'm not sure how simple it would be to implement. Tracking that manually could prove to be a nightmare. Hopefully there is some vbulletin mod out there for this sort of stuff.

My reasoning about this is that those that are interested in actually being a part of the community - they will post and get the name of their companies out more frequently, where it counts and in better light.

Advertising, however, is a form of participation and once a member has earned his way, there is nothing that we can do to prohibit some members the free choice of coming here just to advertise.

As JFSG mentioned, establishing a forced requirement to post will only result in a large amount of useless fluff posts. I'd rather have less discussions with more quality than more discussions with garbage posts in them.

Alas, the voice of reason