I have found that I usually start working on pet projects when I am dissatisfied with my job.
At my last job, I found myself working on several different extracurricular projects at once. I kind of realized that this meant it was time to leave (and do my own startup).
If I found someone who was supremely happy with his job, I would expect that any extra time would be spent at work, either making the product better or developing something else related to that company's business.
With that said, there is nothing wrong with working on a pet project, just that it can indicate something bad rather than something good.
I'd expect someone supremely happy with their standard salaried job wouldn't be first out of the office every night, but I'd be alarmed if they were expected to dedicate their evenings and weekends to making their employers richer.
At my last job, I found myself working on several different extracurricular projects at once. I kind of realized that this meant it was time to leave (and do my own startup).
If I found someone who was supremely happy with his job, I would expect that any extra time would be spent at work, either making the product better or developing something else related to that company's business.
With that said, there is nothing wrong with working on a pet project, just that it can indicate something bad rather than something good.