Letting Go

So, thanks to Pandora, I have come across the song "Letting Go" by Casados.  I LOVE it.  it has a really sweet sound and nice meaningful lyrics.  The singers' voices have a nice melodic sound as well.

I have never heard this song outside Pandora and I have never heard mention of this band anywhere.  I decided to do some 'internet research' on the matter.

I discovered there were quite a few other people in my exact shoes - they mentioned they loved the song but only knew of it because of Pandora.  They wanted to know more.  What are the lyrics?  Who is this band?  Why is this song on XXX pandora station?   Why this song, and not their others?  (presuming they have created more than just one song).

Now, first off, let me say I found this to be a bit of an 'odd fit' for the station I found this on.  That being said, I've noticed a certain frequency of some songs/artists (I know there's a counter argument that this is simply based on what I've "liked".)  However, I assume Pandora to be a 'for profit' organization.  Are there certain artists that have 'agreements' with Pandora?  I assume for every song/artist I discover through Pandora, there must be a ton more that I'm not familiar with that I'm NOT hearing.

Is there a certain reason for "high frequency" artists?  For example, I know offhand I constantly come across "The Bravery" (whom I also do not hear of outside Pandora) and The Strokes (whom I do know of, but don't hear all that much in the mainstream).  I know a couple other Pandora users who have mentioned also constantly encountering these two bands.

Does anyone fully know how Pandora works?  Does anyone have an explanation for why some artists appear a lot and some artists rarely/never do (not that I can cite a specific example here) aside from "this is similar to what I've stated I like"?  Does anyone else love Casados?  Does anyone else know of the band from something besides Pandora?  Are they coming to Chicago for a concert any time soon?  Do they have any other great songs, or are they simply a one "hit" wonder?   What are some "high-frequency" artists you all experience?