The problem here is that Mozilla gets a large part of its income from a company that almost makes the exact same product.
That should make Mozilla feel uncomfortable whenever their agreement with Google is up for extension.
On the plus side, they know they can get money elsewhere if Google were to drop out; they could jump to the Bing camp. That's about their only alternative, though.
Also, their ability to get a good new contract depends heavily on their market share.
Imagine that that software engineer at Microsoft was becoming less productive and knew that Microsoft was hiring young engineers and that there was only one other company he could get a job, and that that company was also hiring young engineers. That should make him worried.
Yahoo and DuckDuckGo give money to Linux Mint for including them in its default Firefox configuration. I imagine they'd be interested in expanding that to all Firefoxen if Google and Microsoft weren't buying.
That should make Mozilla feel uncomfortable whenever their agreement with Google is up for extension.
On the plus side, they know they can get money elsewhere if Google were to drop out; they could jump to the Bing camp. That's about their only alternative, though.
Also, their ability to get a good new contract depends heavily on their market share.
Imagine that that software engineer at Microsoft was becoming less productive and knew that Microsoft was hiring young engineers and that there was only one other company he could get a job, and that that company was also hiring young engineers. That should make him worried.