That is, until now. Developer Taimur Asad has posted a set of instructions to install a multitouch add-on for the Nexus One that will enable the missing pinch-to-zoom and other coveted multitouch gestures in the Nexus One's browser.
The caveats: you'll have to be prepared to root your phone, which gives you complete access to the Nexus One's file system akin to jailbreaking an iPhone. You'll likely also lose your bookmarks and browser settings when installing the multi-touch code.
Still, if you successfully follow the instructions you'll gain access to the sweet multitouch functionality showcased in the video below. Let us know if you have a chance to try this out.
[WARNING]: We're posting this information for your edification only and cannot endorse rooting your Nexus One, as it may violate your warranty and could damage your phone. Proceed at your own risk!