While I think that practice is always good, I cannot ignore the fact that so many people use it for promotion only. Being a designer nowadays means that you have to be able to create and maintain a following, but shouldn't the design-challenge be about design first, and promotion second?

Especially with dribbble; Only few people use it to get feedback, most people use it to promote themselves. I saw a guy once, post a picture of himself on dribbble, announcing that he had gotten a new job at a company. No design, just a selfie.

Those Daily {{term}} Challenges do kind of represent that culture for me. No hate, just my personal view.