If you work for a big enough tech company, like, say, Google or Facebook, it's likely that a lot of things will "relate...to their business." And, note, too, that there's no requirement that you actually know that it relates to a part of your employer's business.
OK if your a semi pro musician but a generic developer sie gig not so much.
Haven't tried it, but I'd be interested to try the argument that the company doesn't want to own my side projects, because liability. If I infringe someone else's copyrights on accident, but the company owns the work, then the company is liable, not me. Sweet protections of corporatization. :)
Or if I make a decisions on a side project that others want to "cancel" on twitter - that'll look bad to the company because legally theyre the owners, right? Wouldn't want the company being to blame for something I did.
(this is usually not enforcable unless you actively build competing services)
What I normally do is ask for an agreement that projects unrelated to my employer's business is ok for me to work on, which I have always been able to get (sometimes they ask for authorization on a case-by-case basis, but usually it's just common sense).
Does it really? I am from Europe and I have lived and worked in 3 EU countries, many of my friends have experience from other countries and I have never heard anyone mention this is. Obviously, my personal experience is limited. In what country do you live if I might ask?
You also bring experience and knowledge to your employer that may benefit them while you're on holiday, or off sick, or even after you leave the company. Maybe we should send them a bill for these incidental benefits?
And European law is just the same.
Instead it should be: "Is it generally easy for employers to get permission from their employees to be assigned all rights for code they write in private?"
Much harder to win in court when they knowingly added a line that lets you work on your own projects.
As long as you're not competing directly with them just leave your day job just as your side project ramps up commercially, and it'll likely never be an issue.
Most are only worried you'll leverage their IP, insider knowledge, steal employers, or somehow cause reputational damage to them - they don't actually want your IP.