Teen superstar singer Justin Bieber has capitalized upon his success to sell everything from toothbrushes to nail polish.

On the tech front, Bieber has invested in companies like Spotify, Sojo Studios and Tinychat. Bieber-backed social media platform Stamped was sold to Yahoo! ( YHOO) last fall. (The "acqui-hire" was CEO Marissa Mayer's first acquisition). Other investors included Ryan Seacrest and Ellen DeGeneres. It's safe to stay that Stamped was star-powered. Bieber is said to invest in dozens of other private companies through his management team.

Although a Bieber shout-out can attract worldwide attention (he has 38 million Twitter followers), investors caution that it may be fleeting. Ben Krall of Metamorphic Ventures says "Justin Bieber tweets ... and all the girls check it out. But it doesn't matter if they don't end up coming back once or twice that month."

Other than e-commerce sites, where first-time visitors can make purchases, these preliminary visits aren't enough to constitute a "user." Users come back to the site again. Says Krall, "usually two or three visits per month counts." Coincidentally, Bieber's debut song was titled One Time.

There's another major pop star named Justin -- Justin Timberlake -- who also has been making venture investments. The superstar recently returned to the music scene with his new album The 20/20 Experience. That ended a seven-year hiatus from making music but Timberlake had been investing in music.

Timberlake backed music education software start-up Miso Media, alongside Google ( GOOG) Ventures in 2010. The company teaches people how to play string instruments, using real-time feedback. Timberlake also invested in social shopping Stipple in 2010, alongside Kleiner Perkins. The triple threat, who played Sean Parker in The Social Network, currently co-owns MySpace. He may be able to "bring sexy back," but can he bring MySpace back?

-- Written by Katie Roof in New York

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