I wholeheartedly agree. I don’t mean to suggest an ignorance is bliss approach, only that if you employer does not have a need to know, you don’t need to go parading around that your employment there has an expiration date of your side project’s profitability.

As for those types of contracts assigning tech IP to $dayjob, that’s what I was alluding to. If you have one of those, unfortunately you cannot start a business without risking $dayjob wanting a piece (or all of it). Regardless of how often they stand up in court or are even tentatively enforced, I wouldn’t want to risk it.

About this type of clauses, I've heard that "well, they are standard and are almost always ignored, as long as you don't cross the line (e.g. code for your side-projects in your day-job office)".

I know this depends on the company, but, as a general rule, are these clauses really taken so lightly?

I was running the engineering group of a VC backed firm when the side project a couple of my people were working on nights & weekends got some great press coverage. By the time it hit TC the Engineers' names were there along with a quote about how their work was supported by their "day job" ... Our VCs took notice and our boilerplate employee PIIA was trotted out to claim rights to the side project. The project was completely unrelated to our line of business BTW...but it didn't matter as the VCs smelled IP value in the press exposure.

I fought the good fight against some silly assertions such as "They could not have built this in so little time without overlapping working hours" but lost the battle when the VCs pointed to the timestamps of some support/feedback comments posted by one of my Engineers on the project's website. He had written those and posted during working hours while sitting in the office of said "day job"

Project squashed, all the IP was rolled up and shelved. It was a bad day.

TL;DR these clauses are typically not enforced because your side project is typically viewed as worthless. If on the other hand your project is seen as a source of value... tread carefully.

The clauses are often ignored by employees with side projects or startups because these clauses seldom cause any harm. But they seldom cause any harm because these side projects or startups seldom succeed. If your startup becomes the next Facebook, everyone will be after you.

In short, by taking these clauses lightly, you are creating failure paths for yourself that begin from the initial light of success. You may not want to kill your big success even before it happens. If your goal is just to create a side income, you would most likely be fine simply because a lawsuit would cost more money than what it may recover, or you may just get some threats/scoldings.

I have heard that if your side project or startup reaches something like $10 million in revenues, your big-company employer actually becomes liable to their shareholders to recover this money from you since it technically belongs to the shareholders.

Some high-profile entrepreneurs have told me that you should not worry about lawsuits as they only come when you succeed and when you do, you have resources to take care of them. But I have also known specific cases of things doing down because of such issues (like the example from etsimm, who also responded to your comment).

By the way, YCombinator submission form includes a question on such IP issues, though I may guess everyone just blindly picks "No issues" for it.

Exactly, when I started looking into doing a few side projects for some extra scratch I went to my employer and had them draft up a letter explicitly releasing me to do side projects as long as it doesn't affect my work or their customers.