I have always followed my instincts while operating my online business. Now that I have a good product to sell, and I have a good affordable price for it, and as I give good customer support, I believe my online work follows a good guidelines pattern. There are no set rules that I follow generally, but if I get across a customer who is keen on making life difficult despite giving every help, then it irks me a lot. I will then take advice from my business friends and also from a lawyer friend (sometimes when absolutely necessary), and find ways to get out of the situation without getting me or my customer into more troubles later on. You may call this tactic a little out of the way, but it helps run the online business.
If one must run a business, online business especially, then there are no hard and fast set rules. Your business comes first, and when you're giving a good product and service, or even running a forum or a site, then you must be able to handle all situations.
Of course, you will find a lot of visitors, members, and potential customers, and even customers who have a scam in mind, and they will try to harm your business. At that point, you're supposed to take hard decisions to save your business and its reputation at 'all costs'.