Google's Android is actually an open operating system for mobile phones and other mobile devices. However, the openness ends at the Market. Various tethering apps (which, for example, turn an Android phone like the T-Mobile G1 into a wifi access point) have disappeared from the Android Market.
Dailytech.com and Techcrunch.com report that Google took this action at the urging of T-Mobile - logical, because with tethering you can simply use your phone's Internet connection to go online with one (or even more) notebooks - although this is not actually intended.
With this, Google is following Apple's bad example. The manufacturer of the iPhone also censors the software that is available via the official app store and has thus created a market for alternative software sources like Cydia in the first place - it remains to be seen whether something like this will also emerge for Google's Android.