Areeq Chowdhury, from WebRoots Democracy, also believes the companies that have joined the boycott will come back.
"The advertising being offered by these internet giants is unparalleled." he says.
"The level of targeting they can achieve is not matched anywhere else, so I find it hard to believe that a lot of them will stop advertising in the long run."
That seems to be what the market thinks, too.
After a dip in Facebook's share price, it's back to pretty much where it was last week.
So, Facebook's strategy so far seems to be working.
The far greater worry is contagion - for example, if users started to leave Facebook and Instagram in large numbers in response to the boycott. But once again, there's little evidence of that happening.
On Wednesday, it was confirmed that Zuckerberg - along with Google's Sundar Pichai, Apple's Tim Cook and Amazon's Jeff Bezos - would testify before Congress in an antitrust hearing later this month.
If the boycott continues to gather force, it could be an uncomfortable encounter, however secure Facebook may feel.