I think Growth and Mobile are the only ones using Extension:Campaigns functionality right now to track account creations, but just in case I wanted to share the fact that for about a week we had data not coming in for most users on desktop. See: http://ee-dashboard.wmflabs.org/graphs/enwiki_campaigns
for a look at this.
This was due to bug 55765, which has been fixed and deployed. If you see any oddities in campaign tracking in the recent past, this bug is likely the culprit.