Generally, Fear. If it’s cheap, Time. Rarely Greed.
The problem with Greed motivation in Tech M&A is it’s too hard to justify the prices. You can’t justify paying 10% of Facebook’s market cap for pre-revenue WhatsApp, or $26b for LinkedIn, just out of Greed.
Yes, Greed drives a lot of tire kicking in M&A, the desire to buy an asset. But most deals for good targets are still too expensive to justify the purchase price on their own merits.
Fear is a much bigger motivator. There is both CEO-level fear and VP-level fear. The CEO fears being overtaken in the longer run by a disruptive technology (WhatsApp, Instagram), and/or by time itself (Minecraft, LinkedIn, Yammer), or by a market that can’t grow infinitely (Demandware, RelateIQ, ExactTarget, Steelbrick). Even tech companies with dominant market shares know that time itself is an enemy.
SVP-level M&A similarly is driven by Fear, but usually fear of missing the plan for this year or next. Engineering is a year behind on a product. Growth is slowing, and there’s no practical way to catch up. Either of the two will drive an SVP to try to buy something to fix her problems her. After all, it’s not her money.
Finally, sometimes, M&A does happen because it’s cheap. Cheaper to buy than build, especially if a great team has been assembled (e.g., Android) or there’s quick early product-market fit. Even, sometimes, because it’s accretive. But tech multiples are so high, and venture valuations so high, that it’s not that common in tech that something you’d actually want to buy is actually cheap.