Facebook turned down Yahoo's $1 billion offer in 2006 and became worth $1.28 trillion. Groupon rejected Google's $6 billion bid and fell to $600 million. The rule: sell if the offer gives you your "first nut"—enough money to feel secure. After that, it's a choice about risk, not math.
The question is, when should you sell? Famously, Facebook turned down Yahoo's $1 billion acquisition offer in 2006, and now it's worth $1.28 trillion. It's probably more than that now. So Groupon declined a $6 billion offer from Google in 2010. Since then, its valuation has dropped to $600 million. Moz declined a $25 million M&A deal from HubSpot in cash and HubSpot stock. In 2014, HubSpot had one of the most successful IPOs of any SaaS company. My take on this is like, you should sell if this will get you your first nut, meaning like it will make you set. Other than that, if you want to let it ride, you have your nut already, that's your decision.
