We discuss what we did over the weekend, and that quite often involves talking about personal projects. Hell, we even may ask each other questions and opinions on sticking points.

Then again, I work for a sane employer and from reading the comments here, most people don't.

Honestly it depends on your employment agreement. If your side project is making money I would not discuss it with anyone at work.

If your employer decides, now or in the future, to take a substantial interest in what you are doing it can cause you no end of headaches. Also please note that it only takes one or two individuals within an organization to stir up trouble. The founder/ceo may not be that interested but if one party along the line decides it is best for that work to cease it will be a HUGE pita.

Not worth it in my opinion. Giving off the impression that you want to leave your job (even if you don't) is a bad look. Find literally anyone else to talk about it with.

I have coworkers with whom we do share information about sideprojects. These are oss tools however and as far as I know we all see it as something done for fun and not monitary gain.

I don't see any issue with it. But of course a lot depends on your sideproject and the environment in which you work

Your employer could argue that you used company resources and company time (i.e. your coworkers' input during working hours) in building the side project and thus under your employment agreement, it belongs exclusively to your employer.

So probably not.

No, never work on your side projects during office hours.

Pros: None Cons: Be sued, company owning your products, be fired

This depends on a great many factors, including how well you know when/about what to shut up, what your specific co-workers are like, the nature of the project, and where you work.

Assume the worst, that they will share every last detail with {any,every}one. Can you live with that? will it jeopardize your side income at all?

Proceed accordingly.

I would avoid it. Better safe than sorry.