Thought I'd try installing Yosemite as a guest OS into a VM (Parallels Desktop 9.0 Build 24237). A little surprised it didn't even find the app, but figured 9.0 might not know what it was looking for. Instead, figured I'd install Mavericks, then try and upgrade with the 10.9 VM's App Store to Yosemite. Might work, might not. However, the function where Parallels "detects" the OS X 10.9 Mavericks installation is also broken. Left for 10 minutes and Parallels found nothing. App was downloaded fresh from the App Store, sitting right there in plain sight in the Applications folder. Rebooted in case the system hadn't registered the presence of the app yet. No change. So, failing auto detection, the KB article describes manual selection and explicitly has this screenshot: That simply does not occur, as shown here: Note the crossed-out-circle pointer as Parallels refuses to use it.
Yup. I struggled with the same issues yesterday attempting to get the public beta installed as a guest OS. No joy at the end of the day FWIW - there is activity on the Parallels Support twitter account indicating that they are aware of the issues and are working on it.
I filed a support ticket for this issue. The workaround is to copy or move the installer from your Applications folder to your Desktop folder. Then try install it.
This doesn't work for Yosemite PB1 as Guest-OS. I've tried the method described on macrumors.com to create a Installer-Image. VMware Fusion 6.04 and VirtualBox 4.3.14 can boot it, Parallels 9 can boot a Mavericks-Installer-Image created with this method, but it's not possible to create a VM with a Yosemite-Installer-Image and the current Parallels Desktop 9.0.24237.1028877. It might work with the Beta of Parallels Desktop 10.
It won't work because Parallels won't let you run forward OSes. Meaning if you're on Mt Lion, and you try to load Mavericks… won't work. A quote from Parallels: The same applies from Mavericks+ At least this is how it appears.
PD10 now allows you to install from the OS X installer apps... it will extract and create an OS X Base System image automatically. Personally tested with Mavericks and Yosemite.