Sean Parker, Napster Co-Founder and Former Facebook President, Joins Twitter; Apologizes to Mark Zuckerberg

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Parker, who sent out his first tweet Monday, already has nearly 19,000 followers and counting.

Sean Parker has joined Twitter -- not in an executive capacity, but as just a regular ol' tweeter.

Parker -- who co-founded Napster and later served as president of Facebook -- sent out his first tweet Monday. In it, he apologized to Facebook CEO Mark Zuckerberg and gave credit to Scooter Braun, a talent manager whose clients include Justin Bieber, for getting him to join the social-networking site.

STORY: Sean Parker Denies Facebook Post Was an Attack on Steve Jobs

"Sorry Zuck, I had to do it eventually," he wrote. "(Actually @scooterbraun made me do it.)"

As points out, it appears that Parker has been planning his Twitter debut for some time, since his account was already verified.

Earlier in the day, he had only 500 followers. By late Monday, Parker was at nearly 19,000 followers and counting.

STORY: Napster to Merge With Rhapsody

Parker, who was memorably portrayed by Justin Timberlake in the Facebook movie The Social Network as a partying playboy, last week revealed that he is reuniting with Napster's Shawn Fanning to create a live video site dubbed Airtime. He also is backing Spotify and has a Facebook charity application titled Causes.

Meanwhile, Napster said earlier Monday that it will merge with competing music subscription service Rhapsody.