"Woo hooooo, woo-hoo-hoo. Woo hoooo, woo-hoo-hoo."

You know the ad: that happy, spastic tune that plays while delighted actors portraying Vonage (NYSE:VG) customers describe their love of the service? Dude in a lobster suit in the background and all that? Well, the reality for Vonage shareholders -- some of whom began as naive Vonage customers -- isn't nearly so joyous.

Today, we find out that Verizon (NYSE:VZ) is doing its part to turn the woo hoo into boo hoo by serving Vonage with a patent infringement lawsuit over its voice over Internet protocol (VoIP) technology. Vonage, of course, says it thinks all is well, and will defend itself.

It's far too early to comment on any of the intellectual property claims in the case, but the takeaway for beleaguered Vonage investors is the same. This is bad news. Not only will this be another big drain on a company that's already burning a quarter of a billion dollars a year, but it also highlights what should be Vonage investors' biggest concern: a nonexistent moat.

VoIP technology is all over the place. Even if Vonage ends up free and clear of Verizon's patents, it still may not have a product that can compete with heavyweights like Verizon, AT&T (NYSE:T), or Comcast (NASDAQ:CMCSA). It may not even stand up to the evolution of Internet messaging, as evident in eBay's (NASDAQ:EBAY) Skype, Google's (NASDAQ:GOOG) chat pretender, or Yahoo!'s (NASDAQ:YHOO) established messenger.

Vonage only looks like a player because it spends so much on those "woo hoo" ads, and sticks a banner on just about every Internet page this side of my dog's blog. It can continue to spend its way to top-line growth, but only if it can raise more dough -- and how likely will that be?

The Street has punished Vonage shares mercilessly. (They've dropped from $17 a stub to less than $10 in mere weeks.) I believe it's only a matter of time before the big telecoms and cable providers squash Vonage entirely. The only real question: How long until the stock is valued accordingly?

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Seth Jayson will be starting an office pool on the Vonage deathwatch. At the time of publication, he had no positions in any company mentioned here. View his stock holdings and Fool profile here. Fool rules are here.