In May 2001, MP3.com founder Michael Robertson sold sold MP3.com to
Vivendi for $US372 million in cash and stock. Of that, how much did
Michael Robertson keep personally? How much was in cash and how much
in stock?

Hello alexanderhilton,

I have done extensive searching for you regarding this question and
here are the results I have come up with:

"Robertson reportedly held 23 million shares of MP3.com as of March 1,
a 34 percent stake. If he still holds that much stock and, like other
stockholders, receives $5 in cash for each share, he could walk away
from the deal with $115 million in cash." (after the sale)
Source: http://alumni.ucsd.edu/headline/sp01/052301_vivendimp3.html

In September 16, 2002 Michael Robertson's wealth was $117 million. 
http://www.fortune.com/fortune/40under40/snapshot/0,15793,38,00.html

It is unlikely that he walked away with just cash because he appears
to have believed strongly in his company, but there does not appear to
be any public information available retarding this.

Even though the stock was worth $2ish, stockholders of MP3.cm were
given the choice of keeping the stock, taking Vivendi Universal stock
(worth roughly $5 at the time) or take $5 cash.

An interesting quote from Michael can be found here:
"Michael Robertson: From a financial standpoint, the company's on
fire. That is what's a shame about the stock price. It's disappointing
for me because I have 300 people who are busting their tails and
they're not seeing the financial rewards yet. I own such a big chunk
that unless it really craters, I'll be fine."
http://www.bankrate.com/brm/news/investing/20001106a.asp?prodtype=advice

It is not as if he won in the end, when his company went public his
worth was about $625 (when he owned half the stock).
http://sicentral.hypermart.net/free/internet/mp3_062299.html

Here is another article that confirms the above findings (approx $115
million)
"Robertson himself is moving into a new role as special adviser to
Vivendi Universal Chief Executive Jean-Marie Messier. Financially,
he's also making out handsomely from the deal. According to recent
regulatory filings, he owns more than a third of MP3.com, which would
make his take from the $5 per-share sale more than $115 million."
http://news.com.com/2100-1023-257993.html?legacy=cnet

I hope this was the type of researching that you were expecting.
Please let me know if you need any clarifications regarding this
answer.

Search Strategy (on Google):

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Excellent answer. Thank you very much.