This is the finale to a three-part series on some serious tech deals that almost went down. Enjoy part I or part II, if you haven’t already.

Yahoo rejected a $44 billion offer from Microsoft.

In the 2000’s, Microsoft was fighting a losing battle against Google’s growing dominance in Internet search and online advertising. It flushed billions of dollars down the toilet trying – and failing – to compete with Google.

Like Microsoft, Yahoo had also invested heavily in online services to no avail. Clearly, no one could compete with Google on their own. Their only chance was to combine forces and take on Google as a team.

Microsoft and Yahoo spent over a year dancing around the possibility of a merger, but they could never agree on a price. Microsoft offered what it thought was enough, but Yahoo always wanted more. In 2008, Microsoft had had enough of Yahoo’s waffling, and put an end to it by making an unsolicited offer to buy Yahoo for $44.6 billion.

Yahoo surprised everyone when it rejected the offer for being too low, claiming that Microsoft greatly undervalued the Yahoo brand, audience, investments, and growth prospects. Had the deal gone through, it could have redrawn the competitive landscape in Internet consumer services.

Twitter turns down $500 million offer from Facebook.

Twitter was just a two-year old company with no revenue when Facebook tried to buy it for $500 million. Twitter founders Biz Stone and Evan Williams declined.

First, the $500 million came in the form of Facebook stock. Stone and Williams wanted cash, and Facebook didn’t have any. Second, Stone and Williams thought Facebook’s $15 billion valuation was inflated. If the offer reflected Facebook’s true valuation, the stocks would only have been worth $150 million, not $500 million, and that wasn’t enough.

Lastly, Twitter’s board simply was not ready to sell. Stone and Williams wanted to build the company up and see it through themselves.

Everybody loves an underdog and Silicon Valley is no exception.There’s something admirable about founders taking big risks and sticking to their guns.

When Domo founder, Josh James, was building his first company, potential investors asked if he was headquartered in Silicon Valley. After learning Omniture was headquartered in Utah, several investors walked away from the deal. In James case, the risk paid off, with Adobe acquiring Omniture for $1.8B in 2009.

So whether you’re building the next billion-dollar social network, or the future of business intelligence, remember fortune—literal and metaphorical—favors the bold.