has added

another huge pile of cash to its bank account, this time in the form of a $100m debt financing from TriplePoint Capital.

The company, which has already raised more than $350m in equity financing from investors such as Microsoft and Hong Kong billionaire Li Ka-shing, says that the money will be used “entirely for servers.

The funding comes on the heels of rumors that Microsoft, which walked away from its attempted acquisition of Yahoo (at least for the time being), has been giving some thought to a Facebook acquisition.

As noted by the New York Times:

“Microsoft’s October purchase of a 1.6 percent Facebook stake implicitly valued the social-networking Web site at $15 billion. Even at the time, some people questioned such an eye-popping valuation. But as the months have passed, the number is looking even more bubbly. And not just to us: Several Web sites this week have questioned the value implied by Microsoft’s Facebook deal. On Friday, PEHub’s Dan Primack suggested it might be ‘one of the worst venture capital deals of all time.'”

Notwithstanding the fact the $240m Microsoft put into Facebook’s bank account wasn’t a venture capital investment, this round of debt financing should only reinforce the increasing skepticism over the company’s path.

I don’t take issue with the fact that Facebook has tapped into debt financing; such financing frequently makes sense and is often cheaper in the long-run than equity financing, especially when used for certain purposes.

What I do take with issue with is Facebook management’s hunger for capital and the obvious growth in the rate that the company’s capital is being burned.

While some might argue that it makes sense for companies that can raise capital to do so now, given the economic landscape and the possibility that money will be harder to come by in the near future, the “raise as much money as you can get” theory does have its limits in the real world.

It is difficult to overlook the fact that Facebook has already raised hundreds of millions of dollars in its latest equity financing rounds.

Just how much money does Facebook really need if it’s simply looking for a comfortable cushion?

Raising a nice chunk of capital to ensure survival during an economic downturn is significantly different from raising an exorbitant amount of capital – hundreds of millions of dollars – when it should, under any reasonable scenario, be unnecessary.

I’d argue that Facebook has done the latter.

The foolishness of this is exacerbated by the fact that while Facebook continues to grow rapidly, it has failed to develop a viable business model that can realistically turn it into a self-sustaining enterprise.

Since the failure of Beacon, whose launch was heralded by Mark Zuckerberg as a revolutionary event for the media and advertising business, the company has done little to indicate that it’s solved the challenge of social network monetization that nobody seems capable of cracking.

Given that Facebook has failed to develop a viable long-term business model and as I have pointed out numerous times before, reportedly generates a significant portion of its revenue from an advertising agreement with Microsoft that guarantees payments, Facebook’s capital binge puts it in a precarious situation.

With a headcount that is expected to more than double in 2008 and much of the money it has raised already (apparently) being applied towards capital expenditures that will merely help the company maintain and expand its infrastructure, I think significant challenges the company faces are being highlighted.

If the company really needs to invest hundreds of millions of dollars into the infrastructure that keeps its service operational yet continues to fail to demonstrate that it can effectively monetize, one should start asking just where Facebook is headed as a business.

Even Henry Blodget, whose foolish SAI25 index pegs Facebook’s value at a cool $9b, is asking questions – and that can’t be good.

Blodget repeats unsubstantiated rumors that Facebook was unable to raise a $500m round of equity financing last year and puts forth a theory of his own:

“According to the numbers Mark Zuckerberg threw out on a conference call last fall, Facebook will burn at least $150 million of cash this year. Given the latest debt deal, we suspect the number is now expected to be considerably higher than that, and Facebook didn’t want its cash balances to drop too low. It couldn’t sell any more equity at $15 billion, and it didn’t want to do a down round, so it turned to the debt markets.”

While I don’t claim to have enough information to make such theories and have no ability to give credence to the rumors that the company was looking to raise $500m from equity investors, I too suspect that things at Facebook aren’t as rosy as they’ve been made out to be.

Perhaps when Mark Zuckerberg comes back from his ‘Vision Quest’ he’ll have the answer to the most important question Facebook has yet to answer: when, if ever, will the company be able to feed itself?