The linuxrc script should have support for booting from USB storage devices, as described by http://gentoo-wiki.com/HOWTO_Gentoo_LiveCD_and_LiveUSB#linuxrc. As USB storage devices continue to gain data capacity and fall in price more users will begin going the route of putting a livecd like system on USB sticks. A kernel line option could be used to signal the linuxrc script that the livecd image resides on USB connected media. Reproducible: Always Steps to Reproduce: 1. 2. 3.
It already works from a USB stick just fine as it is... Remember that Gentoo-wiki is *not* an official site and can (and does) contain invalid information. After all, that page is still claiming the use of livecd-ng, which we haven't been using for 2 years now. All you need to boot from a USB stick is to use "doscsi" at boot.