Microsoft has taken a similar line to Google and Apple on tethering with Windows Phone 7. A report states that Windows Phone 7 devices will support tethering, but carriers will have final say over whether the function is enabled or not.
Tethering, which allows a mobile device to act as a Wi-Fi hotspot, has had a hard time gathering a lot of support by the carriers. Some offer it at an extra charge, others avoid it altogether. It seems that unlimited data plans are just dandy when you're the only one using it, but when five of your buddies are linked in as well it becomes a problem. Rooters and jailbreakers have found various ways around the carrier block on other devices; we're pretty sure that Windows Phone 7 will fall prey to their ways as well.