Comcast ranks first among providers of hosted IP telephony suppliers in the latest Infonetics Research ranking of the top providers in the hosted VoIP, unified communications (UC) and IP connectivity service markets. 8x8 follows closely behind Comcast.

Verizon and West also are among the top hosted VoIP providers in North America, Infonetics Research says. Other firms include AT&T, Bandwidth.com, Broadview Networks, Broadvox, Cbeyond, Cox, Level 3, Megapath, RingCentral, ShoreTel, Sprint, Thinking Phone Networks, West, Windstream, and XO.

What seems to stand out is the extreme fragmentation of the market. Of the roughly 20 firms tracked by Infonetics, less than 10 sell a minimum of 100,000 seats.

Only the several providers at the top of the rankings had at least 200,000 seats in service.

At the end of 2012, the top hosted VoIP providers had over 200,000 seats each while the cutoff to the top 10 was still slightly below 100,000 seat counts, Infonetics says.

So assume the top 10 providers each had 175,000 seats each. Assume the next 10 providers had about 75,000 seats each. That would imply a total of about 1.75 million seats for the top 10, then an additional 750,000 for the next 10 providers, for a total of 2.5 million seats. At $50 a seat per month, that would imply annual revenue of $600 per seat.

So that in turn would imply revenue of about $1.5 billion annually. That’s undoubtedly on the high side, but gives you some idea of market size. For some firms, a revenue stream of $120 million (200,000 seats) would be highly relevant.

For a tier one service provider it probably is not so important, unless the provider thought the business could grow far bigger, perhaps a minimum of an order of magnitude bigger.

In the United States, around 500,000 small or medium businesses used a hosted PBX service, representing an $800 million market, according to Parallels, which made that estimate in 2011.

But it might be reasonable to expect the total market could grow to as much as $4 billion annually, if virtually all current users of business phone systems migrated to hosted IP telephony. Some might argue that is unlikely to happen.

Those who argue along those lines might say there are about 60 million U.S. business lines, and that is addressable market. 

Others might argue the potential market for IP telephony is about 25 percent of total, or about 15 million lines.

Either way, that leaves a market that mostly remains untapped.