OnlyToday - 9:11 pm on Dec 18, 2008 (gmt 0)

...if you're logged into the Adsense console with any address, it's likely you'd also see the personal SERP features...

That's probably it. I log off of my Google account often to use third-party software with it and in particular to avoid coloring the results with my own profile, and I've never seen the SearchWiki icons when logged-off. I'd notice because that would affect the results, how much only Google knows.