I remember leaving one campaign because of a reputation issue, Other than that money is not my consideration not even the number of posts I exceed my post quota sometimes, I just want to be in a campaign where the project I'm promoting is reputable the manager managing the campaign is easy to deal with and the campaign has the potential to last long and so far the current campaign I'm in has all the criteria I'm looking for a campaign.
It's a case-to-case basis for every participant and could be money, number of posts, and reputation. but if you're going to switch from one campaign to the other you better be a good poster and someone who can get into the campaign easily.