an article at TelephonyDiscussion hypothesizes about underlying motivations behind QoS (Quality of Service)

More specifically, QoS from the ITU and ETSI cartels is a reaction to the immediate VoIP (Skype, Vonage, etc.) threat to existing telephony business models. Because voice is today’s killer application it has become the first battleground for operator monopoly business model protection. Expected data revenues are not materializing to off-set declining voice revenues.
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The real problem is no VoIP revenue flows to the operator. Instead, I suspect paying for QoS guarantees will be forced on the customer to bypass secret business model protection plans sometimes called ‘p2p mitigation’; In other words, artificially created IP traffic disruptions. The general idea of these business model protection plans are to add latency and obstructions to network infrastructures to cause quality problems for Skype, AOL, Apple, Google, IBM, MSN and Yahoo (they all have voice as a free add-on) and/or other VoIP activities and in general prevent competition via the Internet protocols unless you pay more for bypassing these artificially constructed latency or congestion constraints. Sometimes this situation is called traffic ‘modulation’ which is really the creative introduction of jitter into traffic flows. This behavior is similar to gang activity that will leave your business alone when you pay protection money.

thanks Lee Dryburgh