Is Silicon Valley in a CFO drought?

This week, Uber CFO Brent Callinicos stepped down from his post in order to spend more time with his family. Last week, Google CFO Patrick Pichette decided his wife and kids could use some more face time. In the past six months, Snapchat and AirBNB have both found themselves without a Chief Financial Officer.

Which begs the question—is there an exodus of top financial talent from Silicon Valley?

Not necessarily, former Trulia CFO Sean Aggarwal told CNBC's "Power Lunch" on Friday.

There are a number of personal and professional reasons a CFO might decide to seek other pastures. "Sometimes, there is no fire and there is no smoke. A CFO has been in the job for several years, they've done everything they can, the company's on a great footing, and it's time to move on," Aggarwal said.

Read MoreGoogle CFO Pichette to retire from search giant

On the other hand, Aggarwal has seen the relationship between a top tech firm and its CFO sour many times, usually in one of two ways: the company falls out of love with the CFO, or the CFO falls out of love with the company.

"In the first variety, the 'we don't like you any more,' what happens is companies tend to hire a CFO a little too early. They've raised a Series B or a Series C, they hire a CFO—and then suddenly things take off, and there is a lot more revenue, hundreds of millions of users, the company is going international—and the complexity can overwhelm the CFO, who was just right for that last stage."

A company that is going through the kind of explosive growth experienced by a hot tech startup can be a challenge for any CFO, and sometimes it is necessary to transition to one with more experience running a larger firm.

"A CFO who was right for when you were a 200 person company with $50 million in revenue is very different than the CFO that's necessary when you are several thousand employees, operating in 30 different countries, several hundred million dollars of revenue. I mean, look at Facebook. The CFO who took them public, who is a fabulous CFO, was not their first CFO, he was not their second CFO, he was their third CFO," Aggarwal noted.

Sometimes, it's the often relentless work culture of Silicon Valley that grinds down the CFO.

"There is a second theme, and it's less frequent, but I do see it. This is when a CFO goes into a situation where you might have a very strong, perhaps a difficult founder, and a difficult culture. A couple years go by, and the CFO has been working 24/7—and things go very well, there's a lot of value that's been created and growth that's been created, and the CFO says, 'Look, do I really need to put up with this any more?'"

When asked about his exit from online real estate site Trulia, Aggarwal laughed.

"We sold the company just last month to our arch-rival Zillow. It's a fabulous merger of the two companies. They've come together, we closed the merger about a month ago. I've done everything I can for Trulia, so I'm moving on to something else."