The Joule, as an example, can boot from USB, uSD Card, and eMMC. It would be awesome if we had "how to" guides on how to boot these different devices using wic. This should start in "Tips and Tricks" on the wiki, but will hopefully be moved somewhere more permanent in the future (yocto web page?). Note: Stephano has access to a Joule and MB Turbot at home. He also enjoys crafting words into coherent bits of portable knowledge.
Both the README.hardware and meta-intel needs to be updated for WIC
Working on this here: https://wiki.yoctoproject.org/wiki/TipsAndTricks/Building_and_booting_for_Joule_or_MinnowBoard
Its looking fairly good now. I'll update the troubleshooting section as I get questions.