I think it's just important to know a little about a wide variety of things as it is to know a lot about a few specific things. Breadth and depth are both valuable.

I ended up doing something similar to what this author tried to do starting in my sophomore year in college (although I didn't have any particular goal in mind when I started). Over the course of about a year and a half, through some combination of classes and my own projects, I programmed Standard ML, Prolog, Haskell, PHP, Ruby, JavaScript, x86 Assembly, Scala, SuperCollider, and Scheme for the first time. At that point, all I really knew were Java and Python.

I think it was an immensely useful experience for several reasons. I've now had some exposure to most/all of the major programming paradigms (and some less common ones too). A month is enough time to begin to get a feel for a language and its idioms, and being able to think and solve problems in different ways will make you a much better programmer even if you do end up working mostly in one or two languages.

Learning how to learn a programming language quickly is also an exceptionally useful skill. New languages don't scare me any more--I can usually learn enough to start hacking on something in a couple of hours, and enough to not be writing completely horrible code in a couple of days. And it's now very rare that I sit down to read a piece of code and can't figure out what's happening because I'm not familiar with the language, which is very helpful when I need to work on something I've never seen before.

That all said, there's a reason I didn't continue doing that indefinitely. Learning one or two languages really well is also very important.

I don't disagree with your premise, but there can be utility to trying out a number of different languages quickly and see which approaches resonate with you. A month with a language won't give in-depth knowledge of a languages' strengths and weaknesses, but it will allow one to move past the superficial differences (syntax, originally intended problem domains) and on to the philosophical ideas behind the language.

Trying Prolog, Erlang, Haskell and Scala in the space of 4 months while trying to solve simple problems (Project Euler comes to mind) should allow one to find a language approach that works. Object-oriented, lazy functional, concurrent or logical, one of those might stick. And if not, there's Lua, Ruby, Groovy, C#, Scheme, Perl6, Python3, Forth, C++, Brainfuck, ...

Each language has a core idea or two that could fit someone's personality. Then, the next year could be spent learning that language in-depth, as you mention. Finally, build upon that experience and re-evaluate the orignal list of languages; JavaScript looks better after Lua, Haskell is Scheme with Prolog-like pattern matching and a generic type system like an advanced C++, Forth and Brainfuck are about a simplicity even beyond Scheme's, etc.