Just as a little background, I co-wrote a book with Dave Mock called Tapping Into Wireless. We've known each other since college and, as you'd expect, get along pretty well. As I expected, Dave put together a compelling bear argument on Vonage (NYSE:VG) -- but I still think he's missing the big picture.

Dave's main attack is that the service is "easily duplicated," and he points to worthy competitors such as Verizon (NYSE:VZ), AT&T (NYSE:T), Comcast (NASDAQ:CMCSA), Time Warner Cable (NYSE:TWC), and eBay's (NASDAQ:EBAY) Skype.

I, however, view this competition as a positive. Other players trying to muscle their way into a space where Vonage has the first-mover advantage suggests that there is something to this technology and market after all.

According to an eMarketer study, the number of global broadband users is expected to grow from 251 million in 2006 to 497 million by 2011. With a sweet spot that big, there's enough room for many players in the VoIP space.

Dave does point out that Vonage is showing lackluster subscriber growth and growing churn. While these are red flags, I still think they're the result of major changes at Vonage. The company is altering its marketing approach, restructuring the workforce, and getting tougher on customer policies. I think these are necessary steps to get to profitability.

As for the lawsuit, Vonage has implemented workarounds that it believes should eliminate ongoing liability exposure from Verizon. So what about royalties for past violations? There is actually good news. Back in April, the U.S. Supreme Court issued a unanimous decision that makes it tougher to meet the standards for a valid patent. The federal appellate courts may interpret this as a sign to be more cautious on patent claims.

As I noted in my bull case, I think there is inherent value in Vonage. It's definitely a true contrarian play and is not for conservative investors, but for those who like to take a flier, Vonage does have lots of potential.

You're not done with the duel yet! Read the other arguments, sound off on CAPS, and vote for a winner!

Fool contributor Tom Taulli, author of The Complete M&A Handbook, does not own shares mentioned in this article. He is currently ranked 2,149 out of 29,896 rated investors in Motley Fool CAPS. eBay is a Stock Advisor recommendation. The Motley Fool has a disclosure policy.