Effectively legal? It is legal. I can privately crawl the web for all references to "John Doe", "johndoe.com", "/u/johndoe28", etc, and save them, because it's all content that John Doe chose to make publically available, whether on his own website or on forum posts or Facebook or what.
There's probably some point at which the ways I use that data can be classified as stalking or harassment, but simply collecting it is allowed.
There are far more sources of information than what John Doe explicitly puts out there. Those are probably the least of his worries.
What about the embarrassing things other people post about John Doe? What if this harms his ability to provide for his family?
What about things fabricated by others to silence or overtake John Doe?
edit: (adding the point below)
Just because it's legal to collect, manipulate, and profit from this mass of information 'somewhere' doesn't mean that concerned groups of people shouldn't try to make that process harder or impossible.
> What about the embarrassing things other people post about John Doe?
Is "John Doe" a politician trying to suppress public discourse about a scandal?
If you do something embarrassing, and people are talking about it, it is absolutely immoral to use government force to prevent people from disseminating information about it.
> What if this harms his ability to provide for his family?
Of course, think of the children. We must suppress any information that could negatively affect a hypothetical child!
There's probably some point at which the ways I use that data can be classified as stalking or harassment, but simply collecting it is allowed.