Does this even mean anything when used correctly? Mark notes that since programmers themselves are on-topic for the site it could be used to refer to questions about beginners...
...But who is a beginner? The kid typing his first "Hello world" program? The freshman about to attend class? The new graduate starting his first real-world project? The polyglot programmer trying to make sense of Ruby? Beginner as a description for a person means very different things in different contexts, much more so than a role like team-leader.
A similar tag is great-programmer, where a disturbing number of the questions tagged are concerned with defining what it means...
Mark argues that beginner could be useful for a person starting their professional life to find questions about other people in the same situation. But Renesis suggests the junior-programmer tag for this, which is probably a better choice seeing as I can only find a couple of questions tagged "beginners" that actually fit this criteria.
Regardless of how it could be used, beginners is primarily used as a meta-tag. They're not questions about beginners, they're questions from beginners! For the vast majority of the questions currently tagged beginners, learning, teaching and education are all better choices.
Let's get rid of it.
