Geforio - I have been using the facebook plugin successfully for months. I am currently using C2 R226 and XDK 3088. I implement through the additions.xml as follows:
<intelxdk:plugin intelxdk:name="https://github.com/cranberrygame/cordova-plugin-facebook"
intelxdk:value="https://github.com/cranberrygame/cordova-plugin-facebook" >
<intelxdk:param intelxdk:name='APP_ID'
intelxdk:value='XXXXXXXXXXXXXXX' />
<intelxdk:param intelxdk:name='APP_NAME'
intelxdk:value='Your App Name' />
</intelxdk:plugin>
where 'XXXXXXXXXXXXXXX' is the Facebook App ID and 'Your App Name' is the name of your App in Facebook. (Facebook Developer)
Let me know if this helps.