Yesterday we covered the Daimler investment in Tesla in some depth, noting that one of the biggest questions was the company's valuation. Given the sparse information revealed at the time, it could have been anything from $100 million to $1 billion.

But Silicon Valley is a chatty place, and now Michael Arrington of TechCrunch has published a rumor number.

His source says Daimler paid $50 million for 9 percent of Tesla, so the company's post-money valuation (as they say in the Valley) is $550 million. Which, as one commenter notes, is precisely two-thirds of this morning's General Motors market capitalization.

As we say in New York, that and two bucks gets ya Starbucks. But TechCrunch is often accurate, so let's look at what it means.

The $50 million from Daimler will keep the company going while engineers and designers from the two companies get down to the nitty-gritty decisions around what parts--or which vehicle--to use as a basis for the 2012 Tesla Model S electric sedan.

The Model S is the make-or-break vehicle that will vault Tesla from being the maker of a few thousand fast, expensive, two-seat sports cars to being a volume manufacturer.

Still, more money will be needed between now and 2012. We wrote: Industry analysts say to launch a higher-volume sedan requires at least a few hundred million dollars. So we expect further investments to be announced over the next two or three years.

The more interesting question to us becomes: Why exactly has Daimler bought into Tesla? Three possibilities come to mind, and they're far from mutually exclusive:

(1)  Daimler wants higher production volumes than it alone expects to generate for the lithium-ion cells from its Evonik battery joint venture.

(2)  Daimler needs deeper design and engineering expertise in the software that controls electric drive and regenerative braking, and buying it in is cheaper than building it from scratch.

(3)  Daimler wants to add a fourth, "green" brand to its stable, which currently includes Mercedes-Benz, Smart, and Maybach. Archrival BMW is known to be contemplating a fourth brand for its as-yet-unreleased "Project i" green car project.

There's much more to be written on this story, which has now become a sweeping saga spanning the globe. Tick it off: Cells from Asia, parts from Europe, brains from Silicon Valley, even a young, charismatic entrepreneur and CEO.

Geez, it's got all the makings of a 21st-century Arthur Hailey novel.

2012 Tesla Model S prototype

2012 Tesla Model S prototype

[PHOTO: Autoblog.nl]