If you are asking that based only on  Lala playing a full song,  remember that is a one time deal . . after that you get the 30 second clip with a pop up for their music leasing option.   

I'm sure you've seen this but other readers may not have . .  
http://www.celestialjukebox.org/2009/10/google-music.html 

From a comment following the article 
<i>" And still, I wonder... whats in it for the artists ? "</i>

And from the article :
<blockquote>Which makes me wonder if he's even listening to himself, or if he hears the real consequence of what he's saying.  Because if this service takes hold, and if vast numbers of users begin to get comfortable with "access" to -- instead of "owning" -- music, that 50% of his business is going to shrink by a factor of 10.  His dollars are about to become dimes. And then pennies.  And then... poof.</blockquote>