Well , Tom Hanks being associated with the App definitely drove a lot of traffic to it. But would you consider this as an endorsement ? Like Britney spears endorsing Pepsi ,where you arent involved in any of the development process and simply show up in an Ad ?

Looks like this is an App that Tom Hanks wanted to make himself out of his love for old and archaic Typewriters* , did not have CS Skills for it , hired an agency and got it done! ( some other articles do mention that he owned a personal collection of vintage typewriters)

Definitely more than an endorsement , but yeah the app has a celebrity appeal to it ( like how Super Copters would now get a lot of press , just because its from Flappy Bird's Dev ) . A fair amount of effort is involved in building one's brand before things you do gain automatic traction.

A buddy of mine was in a non-yc accelerator. One of the questions/goals they had for him was to find his ideal celebrity investor. It's so simple and effective at generating PR (and a little investment cash), I was disappointed I never had thought about it that way before. Not necessarily easy to do if you don't have the right momentum, but effective if you can pull it off.

Interesting ! But celebrity investment doesn't guarantee anything apart from a lot of initial press and traction,do they ? Those startups continue are vulnerable to the same failures like any other. Ashton Kutcher invested in the social flirting app which failed to take off , Leonardo Di Caprio invested in Mobli (which isn't big right now either) and a few others. If there is no alignment of the celebrity's existing brand & image to the startup they invest in , the value seems to be strictly initial publicity.