Two weeks after laying off 30 percent of his employees, Jaxtr CEO Konstantin Guericke finds himself out of a job. He is being replaced by vice president of engineering Bahman Koohestani (former CTO at Cyworld and Orbitz), who will be acting as “interim” CEO.

Jaxtr offers VoIP calls to both your regular and mobile phone. Its last round was a $10 million Series B in June. Investors include Lehman Brothers Venture Capital (yup, they are still around), August Capital, Mangrove, Mayfield, DFJ, and angels Ron Conway and Reid Hoffman. (Guericke was part of the founding team at LinkedIn).

The company is obviously going through a rough time, but Koohestani still spins it as a “very healthy” business. He offers the following partial stats:

Jaxtr, a startup that offers VoIP serivce as well as a social network, has laid off 13 of its employees in light of the current economic climate. As of June 2008 the company had 35 employees (we’ve asked the company for the current count).

CEO Konstantin Guericke says that the company is well positioned to weather the economic downturn, as it has not yet spent any of the $10 million Series B round it raised in June. He says that along with the company’s revenue streams and growth, the cash will be enough to sustain the for at least 18 months, and that it will continue to hire for essential positions like web developers and system administrators.

As Lehman Brothers sells off its assets following its bankruptcy, there is still a big question as to what will happen to its venture arm and, more importantly, how any change in ownership will affect the companies in which Lehman Brothers Venture Partners holds a stake. Like many investment banks, Lehman got into venture investing in the mid-1990s to try to capture some of those venture returns. The investment management group that it was a part of was sold off to Bain Capital and Hellman & Friedman on Monday, but the venture arm was not part of that sale. Instead, Lehman Brothers Venture Partners is trying to spin itself off as a separate venture firm with about $800 million in assets.

But if it cannot do that, it will either go to hungry creditors or a financial buyer who may be more interested in liquidating the fund than in nurturing the startups in its portfolio. Those startups include Kayak, SearchMe, Jaxtr, Endeca, and about 80 more (A partial list from CrunchBase is below. Other than comScore, most are still private).. They could wake up tomorrow and find that they have a new shareholder who is even more impatient for a quick exit than its existing ones. It’s like being an orphan and wondering who your next foster parents will be.

Jaxtr is unveiling premium memberships this evening, making it easier for users of the web-based VoIP service to make long distance and international calls. The service – which includes widgets that users can put on their social networking profiles to enable friends to call them – previously employed a credits system, requiring users to reload their account each time it emptied.

While the credit system isn’t disappearing, the new premium memberships will offer most users a better value according to CEO Konstantin Guericke. In an interview last week, Guericke noted that “in exchange for users committing to us, they will get rates that are 20-30% lower than buying calling credits a la carte.”

For example, the lowest level Jaxtr plan, priced at $2.95/mo, gets you 350 minutes of calls per month, while when buying a la carte, 400 credits will cost you $5.00. Jaxtr is also introducing two other membership levels – $7.95 for up to 1,000 mins/mo and $19.95 for up to 2,500 mins/mo.

In turn, Jaxtr gets more predictable subscriber revenue, which it projects will make the company profitable in the second half of 2009. Jaxtr currently claims more than 10 million members, and also generates revenue through advertising via its Café Jaxtr social networking product.

Overall, Jaxtr is emerging as one of the better positioned companies in the social networking space amidst the current economic slowdown. The hybrid business model of subscriptions and ads is akin to that of LinkedIn – where Guericke was a co-founder – and provides Jaxtr with flexibility should advertising revenue slow down significantly. Meanwhile, the service saves customers money through its low cost international calling – something more and more businesses will be looking to do as budgets get trimmed.

On the other hand, web-based VoIP hasn’t been a slam dunk for everybody. Earlier this year, we witnessed the implosion of one of Jaxtr’s biggest competitors – Jangl – the team of which has since been absorbed into Jajah. Nonetheless, Jaxtr appears to be executing well, and adding premium memberships is a logical step in the often elusive march towards profitability in the social networking space.

—Related Articles at Mashable | All That’s New on the Web:Jaxtr Reaches 500k, Expands to 18 More CountriesJaxtr Grows 10x; 5 Million Users in 5 MonthsJaxtr Makes International Calls Cheap and Easy; Raises $10M to Go GlobalJaxtr Raises $10M in Series A Round: Reaches 1 Million UsersWhere Does Ribbit Fit in the Web-Based VoIP Universe?Jajah Introduces Buttons: Widgets for Toll-Free CallingRibbit to Launch Flex Developer Tools for Voice & Contact Management