> The companies with dual shares seem to do well
The scenario in which dual-share structures can be a problem is if things don't go well. Specifically they greatly limit the shareholder's ability to protect their investment by removing the CEO. That's why it's considered poor governance.
I'm imagining a world where you don't get to fuck up as bad as FB did spending multiple years chasing the Metaverse while letting their platform rot, relying purely on plateauing ad revenue.
The counter argument is that active external governance can be bad for the long term prospects of the company. Optimizing for quarterly results, activists investors threatening and getting sweetheart deals that are good for them and bad for the rest of the company.
In the end it comes down to leverage, Zuck famously didn’t sell early so people were pounding down the door to invest when they finally got the opportunity.