They are hard to regulate and I really doubt governments have either the willingness or the competence to do so effectively. The businesses are very heavily motivated to find ways around regulations, or manipulate them to to their advantage.
Regulation is a very poor substitute for competition, and for well informed customers.
Some of what I said in this comment is relevant: https://news.ycombinator.com/item?id=45780529
> Regulation is a very poor substitute for competition
I've been following tech for my entire adult life. For more than 30 years now, competition or waiting for customers to become informed has never worked.
The only tools we have against mega corps are the ones the EU is currently applying via DMA and similar. But it will take a global effort in order to permanently shift priorities towards "earning money while doing the right thing" (as opposed to "earning money" state of today).
Corps like Google, Apple and friends are more similar to countries than businesses. The only problem is, international law and political pressure doesn't work on them as they're similar to countries governed by cartels.