Recently, it came to light that IRS internal policy allowed agents to access taxpayer e-mails without obtaining a warrant. At the time, the Acting IRS Commissioner Steven Miller (who has since resigned) said that he was not aware of any such incidents occurring, and the policy would be revised. But no promises were made about messages on social media sites such as Facebook and Twitter.
The upshot: Be careful what you display on the Internet for all the world to see. Ill-conceived postings could come back to haunt you.