No amount of regulation will save users from installing a hundred of toolbars if they want to do that.
But it will hinder legitimate programmers from publishing useful software (especially free and open source software).
Would you except restaurant-goers to be liable if they get poisoned? Now compare that to picking your own mushrooms, or dumpster diving. Part of the deal when you start charging for something, has to be that the customer can expect the product to… work.
How are users supposed to vet all the software we run? How are you supposed to know that a compiled binary from Wacom snoops on your computer? That gmail - or, worse, some random startup has no security vulnerabilities?
Users don’t have time to read the source code for every product. Even if they did, we don’t have the source code for most software on our devices. And even if we could get that, we don’t have access to any of the code running on someone’s web server.
Saying users are responsible is the same as saying nobody is responsible.
The only way a user can take responsibility is to refuse to use products and services from startups & young companies who don’t have a reputation yet. And if people feel the need to start doing that, it’s bad for everyone.