Interesting – Google are now sending out alerts to Webmaster Tools users if they find you running an old install of WordPress:
Subject: WordPress Update Available
Dear site owner or webmaster of http://qualitynonsense.com/,
Your site appears to be running an older version of WordPress. Google recommends that you update to the latest release. Older or unpatched software may be vulnerable to hacking or malware that can hurt your users. To download the latest release, visit the WordPress download page.
If you have any additional questions about why you are receiving this message, Google has provided more background information in a blog post about this subject.
Best wishes,
Google Search Quality Team
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