For Vonage, things have gone from bad to worse. On Sept. 25, a jury found that Vonage infringed on Sprint Nextel's patents. It asked Vonage to pay $69.5 million in damages and a 5% royalty rate for future use of the patented technology. Sprint may also seek an injunction against Vonage; Vonage say it will appeal. So, what does this mean for Vonage? Basically, Vonage will need to find its way to break even faster now, as its cash has taken a major hit, and it can't afford to lose money for much longer.

Here're some back-of-the-envelope calculations. Vonage will have to pay some $69.5 billion in damages to Sprint. In addition, since spring, it's placed into escrow or issued a bond for some $90 million related to a patent-infringement case it lost to Verizon (a decision on an appeal is expected any day now). That adds up to $159.5 million. Plus, Vonage is obviously paying lots of legal fees. And Vonage is still losing money: It lost $34 million in the second quarter alone.

So, let's look at Vonage's cash. At the end of the second quarter, the company's cash and equivalents totaled $344 million, which included $66 million of restricted cash used as collateral for the Verizon bond. If we subtract from that the various royalty payments and jury awards/restructed cash, Vonage has about $184.5 million in cash and equivalents to work with.

Assuming Vonage continues to lose money at the current rate of $34 million per quarter, the company can last for a little over five more quarters.

This is a very rough estimate, of course: Vonage's expenses will rise as it starts making royalty payments to Sprint. The outcome of the Verizon case can tip the scales one way or another. Thanks to recent staff cuts, overall expenses may fall. But one thing is clear: Vonage will have less financial flexibility now, after the Sprint loss.