What is Twitter worth?

Yesterday's big news story, at least in valuation circles, is that private equity investors have invested $ 100 million in Twitter for a roughly 10% stake, suggesting a billion-dollar valuation for the nascent company.
http://blogs.wsj.com/deals/2009/09/24/breaking-news-twitter-to-raise-100-million-from-insight-t-rowe-price-other-investors/
Twitter, for those who may be living in the middle ages, has about 30 million members who post short messages (less than 140 characters) that other members can read (if they choose to follow your tweeting). Every celebrity (sports, politics, media) seems to be tweeting now. There are three questions that came up after the story:

1. How did the equity investors in Twitter come up with the $ 1 billion value?
We assume degrees of sophistication to private equity investors and venture capitalists that they usually do not possess. In my experience, venture capital valuations often represent back-of the-envelope computations with hefty discount rates (target rates if 30-60%) taking care of the uncertainty. I was not privy to the valuation of Twitter but I can read the tea leaves and guess how they valued the company. A few months ago, Facebook (a company that Twitter aspires to be at least in the new term) raised equity from a group of Russian investors, who attached a value of $ 6.5 billion to the company. At the time. Facebook had approximately 200 million members, which works out to about $32.5/ member. As of last week, Twitter had about 30 million members. Applying the $32.5/member to this estimate, I get $975 million (suspiciously close to $ 1 billion). This may be pure coincidence but given the pull towards relative valuation on the Street, I think it may explain the valuation.

2. Could Twitter be worth $ 1 billion?
"Could" is a very weak word. Of course! What Twitter has going for it is the numbers. With 30 million members, all I need to be able to do is to generate a small cash flow from each one and the valuation will be justified. A billion dollar value for a firm requires that the firm be able to generate about $ 100 million in operating income in steady state. (I am applying a 10% cost of capital, typical of mature firms, and assuming zero growth). With 30 million members, that works out to $3.33/year from each member. If you are a Twitterer, the question I would have for you is this: Would you be willing to pay an annual membership fee of $ 5 or $ 10 to follow your favorite celebrities thoughts? If the answer is yes, the billion dollars is paid for... If not, I will keep looking...

3. Is Twitter worth $ 1 billion?
Interesting question. As an ongoing business, I don't think so and here is why:
a. You don't buy a business that does not have a business model yet. Twitter has a lot of members but it really does not know how to make money of these members (yet). Advertising alone will not do it. Any blatantly obvious way to earn money (such as charging per tweet) will very quickly decimate the membership. So, where will the additional profits come from?
b. You are buying a business that may be a fad, at the peak of its faddishness: Twitter is hot right now, because it is in the news. However, most of the tweets that I read are inane: it is tough to be profound 24 hours a day and to express that profundity (is that even a word?) in 140 characters.

However, I think that you can justify a $ 1 billion value for Twitter at least to some investors and that is to think of it as an option. What you are buying then, when you buy this firm, is access to 30 million potential customers, who may not know each other but are tied to one another. There are at least two types of investors who may find this investment appealing:
a. A firm with deep pockets and products/services that may be appealing to the membership of Twitter. The 30 million members of Twitter tend to be techno-savvy, older than Facebook members (on average) and well off. They also tend ot think well of themselves or at least their opinions. To illustrate, Microsoft did take a position in Facebook a few months ago and I can see other companies with products (especially in entertainment) do the same with Twitter.
b. Risk money: While no investor in his right mind should be investing the bulk of his portfolio in Twitter, it may be a good investment for risk money, i.e., money you want to invest in high risk, high reward investments and are willing to lose. Spreading your bets across multiple investments like Twitter may create a portfolio that has a good risk/return trade off, especially if you can bring some selection acumen to the process.

P.S: Facing the scorn of my teenage daughter, I created an account on Twitter about 6 months ago. I have never tweeted but I have 228 followers. Scary!!!!