I took a year off to travel before my current job. Best thing I ever did. Before leaving, I made sure I had several standing job offers. Get your foot in the door when you're in a stronger position. Do it for your own peace of mind if nothing else. You don't want to spend half of your sabbatical worrying about what to do when it's over.
You found companies willing to wait a year for you to start? That's surprising, I wouldn't have guessed that would be easy to do. I'm thinking about this myself, but I'm looking to join a startup and I can't imagine that would be feasible given that a year is a long time for a startup.
It is absolutely still a thing. Since the current top comment (from cletus) mentions working at Google I'll relate a story from when I interviewed there. From what I understand, I made it pretty far in the process (to the "executive committee review") and that's when they asked me to explain a gap in my resume. They pressed me for a detailed breakdown of what I did during the gap and the reasons behind it, and said that they take it seriously. This was after 8 technical interviews and after I'd passed their hiring committee. I didn't get the job, although I suspect that this was not the reason. I'm sure experience varies here, and this would likely be less of an issue at a startup or other small company where a record of getting shit done is more important, but it's worth noting.
I would recommend that if you take time off for whatever reason, prepare for questions like these and be ready to provide a succinct and compelling explanation at the drop of a hat, because being blindsided isn't fun.
Jeez, good to know. As mfalcon mentioned, freelancing would be a good fallback, but you'd still have to talk about what kind of work you were doing etc.
Unfortunately, yes. Employers, and the non-technical gateways in particular, still have the mindset of "reject for anything, weeding people out means I'm doing my job!"
Make yourself look so valuable that they wouldn't dream of rejecting you for some invented reason. If front-line resume screeners are the issue, get an existing employee to submit your resume and vouch for you and get buy-in from their boss. That way HR can't reject you on a flimsy basis.
If you're a programmer and you're taking time off to learn and build things, then I can't see how it could hurt you with future employers.
"Why did you take the time off?"
"I was building this thing that has since been forked 200 times on Github and is running in at least a dozen shipped projects"
"Ok then"