Charlie Sheen now for fastest to reach 1 million followers on Twitter, but another celebrity who made headlines back in 2009 might want to keep a closer eye on his account.

Twitter enthusiast and actor Ashton Kutcher, who now has almost 6.4 million followers, had his account hacked while attending the TED conference.

"Ashton, you've been Punk'd. This account is not secure. Dude, where's my SSL?" reads the most recent tweet on his account.

The hacker apparently posted another tweet that said "P.S. This is for those young protesters around the world who deserve not to have their Facebook & Twitter accounts hacked like this. #SSL" - but that has since been deleted.

The hacker was apparently trying to make a point about lax security measures on social-networking sites. As Sophos's Graham Cluley points out, "tools such as Firesheep make it child's play for anybody sitting close to you to jump onto your Facebook or Twitter session if you're using unencrypted WiFi without an SSL connection, for example at a free WiFi hotspot."

Insecure Twitter and Facebook accounts can be tempting for cybercriminals who want to take advantage of the millions of people following celebs like Kutcher, Cluley said. "We should just be grateful that on this occasion the hack appears to have taken place to promote better awareness of the need for better security, rather than with more malicious intent," Cluley wrote.

He said it would be "great" if Twitter "forced the use of HTTPS at all times."

HTTPS keeps data encrypted as it travels between your Web browser and servers and is mostly used for things like banks and credit card company Web sites. Sites that deal with sensitive personal information have typically used HTTPS during the sign-in process to protect password information and reverted back to HTTP afterwards because full encryption can sometimes slow down your experience on that site. and have optional full HTTPS and last year implemented full-time, opt-out HTTPS.

Last week, New York Sen. Charles Schumer on Monday called on Internet companies like Amazon, Twitter, and Yahoo to in order to prevent hackers from gaining access to personal information over Wi-Fi networks.

In a Wednesday tweet, Twitter said "users can use Twitter via HTTPS ... We've long been working on offering HTTPS as a user setting & will share more soon."