Coming soon to Google Chrome: use your extensions in Incognito mode!
At least your extensions don't work for now.
Soon enough you'll have the ability to specify which extensions you want Google Chrome to allow while you browse Incognito. The change has landed in recent Chromium builds, and I have no doubt that we'll see this make the jump to Chrome's developer and beta channels fairly soon.
While it will be nice to have certain extensions available -- like LastPass (so I don't have to type in all my passwords) or ExtensionFM (so I can listen to my music library in the cloud) -- it's important to remember that some extensions may do things that you're trying to avoid during private browsing sessions. In fact, Chrome/Chromium will spawn an alert saying "Chromium cannot prevent this extension from recording your browsing data" when you place a check in the allow box.
For now, you'll need to download a build from the Chromium BuildBot stash to try this out. So far, so good. I haven't experienced any (additional) instability or crashing due to enabling a few extensions in Incognito mode.