PPK over at the QuirksMode blog recently wrote a rant titled The iPhone Obsession where he berates developers for focusing on the building mobile sites that are targeted towards well on the iPhone. To make his point, he uses the following statistics

Stats

Let’s illustrate that last remark with some smartphone sales stats:

1. Nokia: 39%
2. RIM: 20% (BlackBerry)
3. Apple: 15% (this 15% is obviously far more important than the previous 59%)
4. HTC: 5%
5. Other: 21% (Samsung is expected to make a major jump this year)

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Source: Morgan Stanley Mobile Internet Report (48Meg PDF) p. 160

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And here are the smartphone OS stats, also from Tomi Ahonen (whose blog I highly recommend, by the way):

1. Symbian: 45% (all of Nokia plus a bit of SonyEricsson and Samsung)
2. BlackBerry: 20%
3. iPhone: 15% (this 15% is obviously far more important than the previous 65%)
4. Windows Mobile: 6% (HTC, Samsung, SonyEricsson)
5. Android: 4% (HTC, Samsung, SonyEricsson, Motorola, Google)
6. Other: 10% (Various Linux builds, Palm, as well as really obscure stuff. Will be reinforced by Samsung Bada during this year.)

Despite the platform having only 15% sales market share we all want our mobile websites to look exactly like an iPhone app and we only want to use iPhone features.

Although these statistics seem persuasive they are actually totally useless when it comes to arguing the point of which browsers mobile developers should target. Ownership of a mobile phone doesn’t directly equate to using it for browsing the web. The important metric is the smartphone OS breakdown among people who actually use the mobile web on their phones.

You can get these stats easily from AdMob's mobile metrics report which is based on measuring ad impressions across various mobile sites across various smartphone OSes. These metrics paint a very different picture from the sales data as shown below

According to these stats, the iPhone OS is actually the major source of traffic for the mobile web in most continents except for Africa and Asia. What this tells you is that developers aren’t being stupid when they try to ensure their sites work well on the iPhone.

That said, I agree that it is a bad idea for developers to specifically target features of a particular browser versus using web standards. However that is different from making sure your site works well in the most popular platform used for browsing mobile websites in your particular market.