[linuss]

I agree that for most developer roles most of these are definitely not necessary. I do know from personal experience that learning things that are far removed from any of the regular projects you're working on can provide valuable insights. The thing with these projects is that it's really difficult to know what you don't know yet, and so implementing something that is far removed from your day-to-day workings can provide you with insights that might help you, even though it seems completely alien.

Also, these projects are intended for self-study. Building an entire product from top to bottom is indeed a very valuable skill, but hopefully one you learn on the job.

[mikekchar]

Actually the number of opportunities you have to build something from top to bottom are not that numerous. In my 30 years I can think of 4 non-trivial projects off the top of my head. In fact I often advise programmers to have a side project where they get to make all the decisions and see how it works (or doesn't). One of the side benefits is that it tends to make people much less "my way or the highway" at work because they have somewhere that they can express themselves fully.

[spacemanmatt]

I have been recommending side projects on a similar basis for a while. I usually emphasize learning under the condition of leisure rather than schedule pressure, to enhance focus on good design and allow for a depth-first learning style.