For the record, I didn't invest any money in Groupon.
Groupon asked me to be on their board of directors. Compensation for that position was paid in options. That's why I have options/stock in Groupon, not because of an investment.
As far as angel investing goes, I have not made any angel investments to date. The only private company I've ever invested in is my own company, 37signals. That's not to say I wouldn't invest in another private company, I just haven't so far.
