Unfortunately, the biggest challenge to the total adoption of VOIP isn't the complex technology, or the lack of experienced implementers, or even compelling business cases. It's regulatory hoopla. VOIP is simply illegal in an astonishing number of countries, while the rest are mired in enough red tape to often negate the cost savings.
I suppose I can't blame the incumbents from trying to defend their oligopoly (e.g. http://www.fcc.gov/Bureaus/Common_Carrier/Other/actapet.html) but it has led to a regulatory environment that is volatile, complex, inconsistent and confusing. Worse, no two countries have the same telecommunications laws, so even mid-sized companies need to seek legal help before they connect to any foreign country. In fact, a quick search on the Internet turned up entirely too many stories of companies having their VOIP gear confiscated because it is simply against the law.
While I am not a lawyer, and cannot dispense legal advice, as an example I would like to call your attention to one of the more popular destinations for VOIP circuits: the UK.
The UK Office of Telecommunications has a document that provides a relatively up-to-date FAQ for regulations of VOIP, which you can find at http://www.gipiproject.org/telco/020402oftelguidelines-voip.pdf. The main Web page is www.oftel.gov.uk.
Interestingly, in this document, the Oftel even claims to have the power to regulate your QoS!
You'll also want to check out the UK's Telecom Regulations 1997, a dry read to be sure, but similar to our own, unfortunate Act of '96. Find it at http://www.hmso.gov.uk/si/si1997/97188601.htm.
Of course, these telecom regulations aren't the only ones you have to watch out for. As an informed reader pointed out, organizations doing VOIP or IP Telephony in the US of A also need to be familiar with the Americans with Disabilities Act (ADA). For companies subject to this regulation, your telephony solution also needs to meet certain guidelines for accessibility to disabled persons. This includes the blind, and the deaf, and means also complying with regulations for such things as public telephones being a certain height and unobstructed to people in wheelchairs.
Also interestingly, Web pages were also recently determined to be subject to the guidelines of the ADA. So pay double attention if you're converging your IP Telephony and the Web.
Thomas Alexander Lancaster IV is a consultant and author with over ten years experience in the networking industry, focused on Internet infrastructure.