The Internet abounds with policies. There are policies on name
allocation, policies on address allocation and policies on routes.
There are also policies on use of network resources (bandwidth!),
since this is the most precious resource that costs money. Your
internet provider will make you aware of policies relevant to your
business. A common misunderstanding about the Internet is the belief
that you cannot use it for commercial traffic. This is not the case
at all. What is the case is that some parts of the Internet are part
of government or state organisations infrastructure (e.g. the
academic parts) and are typically paid for for that use, and on a
per usage basis, or simply for say year round access. Sometimes the
rates negotiated for a large organisation's collective access are
specifically on the basis that it doesn't sell on usage.
In times gone past, commercial use was seen as potentially undermining
the quality of those parts of the network, or else of undermining the
justification for state subsidy for access to the net for these
agencies. 
There is also the social phenomenon that has arisen called Netiquette which includes a whole range of unwritten rules about what is and is not acceptable use and behaviour ``on the net''. Unsolicited posting of advertising is certainly regarded as verboten. On the other hand, appropriate use of non-invasive advertising (bulletin boards or WWW pages for the express purpose of) is certainly not frowned on.