Aside from the already mentioned predatory nature of Yelp (I personally watched a smear campaign happen to a bar I played piano at in another life), IANAL but I

Aside from the already mentioned predatory nature of Yelp (I personally watched a smear campaign happen to a bar I played piano at in another life), IANAL but I think raising money for your business could have all sorts of unintended tax and legal ramifications the business owners did not sign up for. Also, having one business have one of these campaigns but not, say, a competitor could be seen as a sign of weakness. Conversely, it could be seen as anti-competitive behaviour