A number of financial analysts have been raising their expectations about YouTube‘s revenue in recent weeks, under differing presumptions about how fast the company’s various new ad formats are starting to make money. But based on what we’re hearing about YouTube and some international rivals, the growth in optimism seems to be outpacing the growth in revenue.

Today, Lehman Brothers’s Doug Anmuth projects that YouTube will bring in somewhere under $200 million for 2008, about double analyst projections last fall. Meanwhile, Forbes and Citi have recently projected the company’s 2009 revenue to be $350 million and $500 million, respectively. (Silicon Alley Insider has more on the numbers, here.) Remember that this is revenue — not profit after paying for video hosting and other expenses.

One immediate problem with the analysts’ analysis is that each assumes different revenue paths to justify the growth. Display ads are the cause, Citi thinks, while Lehman’s Anmuth sees dollars from in-video overlay ads and the new ability for video creators to sell their own ads.

But I’ve heard from others in the industry that YouTube is only breaking even.

Also, hosting costs are high for any online video company. For example, I hear Chinese online video sites like Tudou, Youku and 56.com have been spending $1 million to $2 million a month in hosting costs. As YouTube is the largest video site in the world, it likely is spending at least that much, even with Google’s optimized, cheap server farms to support it.

Tudou’s funding deck: A window into what video sites themselves are thinking

Meanwhile, for sake of comparison, here’s a behind-the-scenes look at numbers from Tudou, which goes up against Youku as the largest video site in China. Note: Tudou gets around 60 million unique visitors a month, from what I hear; for a reference point, YouTube had 83.7 million U.S. visitors in April, according to comScore.

A source on this side of the Pacific has sent me the deck that Tudou used to raise a recent $57 million funding round. The deck, created last fall, shows the Shanghai company’s making $44 million this year, $123.7 million next year, and an even $200 million in 2010.

True, the size of the Chinese ad market, while growing, is still much smaller than the U.S. ad market. And, both the Chinese internet’s online video ad formats and its third-party traffic measurement are less developed than in the U.S. Fewer ad dollars are available to Tudou than to YouTube.

(Note: There are other factors facing Tudou, but not YouTube. I also hear a rumor it was very close to being permanently shut down by the Chinese government in March due to censorship before one of its investors with government connections personally intervened on its behalf.)

So assuming Tudou’s self-assessments are accurate, one would still expect YouTube to bring in revenue at a faster rate than Tudou because of monetization issues in China, even though Tudou is relatively large compared to most YouTube competitors in the world.

But maybe not. Tudou itself told me last month that it has focusing on monetization for many months, and it believes its efforts — which span pre-roll, post-roll, splash page ads, viral ads and others that YouTube has been experimenting with — are as innovative as any rival. It also told me that it still isn’t seeing anything exceptional on the revenue front.

Tudou is one example, but I know of no other online video site that is seeing the sort of revenue growth that the analysts are now expecting out of YouTube. Add this fact with the rumor that YouTube is only breaking even, and the analysts’ contradicting rationales for revenue growth and the sum is this: The analyst estimates from last fall, ranging from $75 million to $90 million, still seem the most probable.