Is SIP only for enterprises?

Can SIP be used for consumer market devices or will it only exist in the enterprise domain? This seems like an easy question to answer - surely it is suitable for consumers as well.

I met with a customer last month who is working on a videophone consumer product. Their company is specifically looking for a proprietary signaling protocol. The reason for this is:

SIP is good only for the enterprise market

I know for a fact that SIP is prevalent in the consumer market and will become even more so in the near future due to the following reasons:

• Packet Cable is using SIP for its cable modems.

• TISPAN, dealing with PSTN (Public Switching
  Telephony Networks) is adopting IMS (which is again SIP) for their future phones. I’ve seen several operators already looking at this direction.

These reasons do not allow for equipment vendors to develop a consumer product that is not sold through the operators today, which in turn makes it less of a consumer market for the vendor.

Digging a bit further, it seems that the reason they came to this model is because of the existing free internet VoIP services which do not use SIP.

Sounds reasonable, but this is far from the truth.

Two months ago, VoIP-News published a list of applications, tools and services that use VoIP as a mainstream application. Looking at that list, I have found that at least 27 of the products are actually using SIP as their protocol of choice. Many of them are providing services directly to the end-users. 5 of the other products use proprietary protocols (1 based on SIP P2P and 3 are Skype) and the rest I simply could not find out.

SIP in the consumer market

I have the feeling that the unknown products use SIP as well because there is simply no point in using anything else these days.

I have already stated my views about the two emerging VoIP markets - enterprises and consumers. At the moment I believe that both are driven by standard based solutions rooted in SIP.