Stern-Gerlach and Hund's second rule According to Hund's second rule, the spin tends to be maximal. 
That would, in my understanding, imply that, regarding the Stern-Gerlach experiment, the important electron in a silver atom has spin 1/2 (or "up"). This should hold for all atoms.
Every atom would have the same spin magnetic moment (smm) - because the smm points in direction of the spin - and thus be affected by the B-field just like any other atom.
But, if every electron has the same smm w.r.t. the magnetic field, why do we get two "blobs" on the screen and not just one "blob" above or below the z-axis?
Where is the error in my thought process?
 A: When we say that the spin of a silver atom (in a magnetic field) is $+1/2$ or $-1/2$ we mean its component in the direction of the magnetic field (referred to as $S_z$) is $+1/2$ or $-1/2$. The magnitude of the spin is the same in both cases, it's just the direction that's different.
Hund's rule just tells you what the magnitude of the total spin is, and doesn't say anything about the direction that spin is pointing. For example with two unpaired electrons Hund's rule tells us the total spin will be $S = 1$. However put that atom in a magnetic field and you can have $S_z = 1$, $0$ or $-1$.
The two blobs in the Stern-Gerlach experiment correspond to the electrons with $S_z = +1/2$ and $-1/2$, but all the electrons have the same total spin $S = 1/2$. The two unpaired electron system with $S = 1$ would give us three blobs corresponding to $S_z = 1$, $0$ and $-1$.
A: Although an electron is referred to as a spin 1/2 particle, it doesn't mean it is in a spin 1/2 state (confused yet?).  A spin 1/2 particle has two states it can be in. It can be +1/2 in which case it goes up Stern-Gerlach experiment, or it can be in the -1/2 state in which case it goes down.
If there are two unpaired electrons in a molecule, then it is called a spin 1 molecule and has three states (+1, 0 and -1).  If the 2 electrons are both spin +1/2, the molecule will go up, if 1 electron is spin +1/2 and the other spin -1/2, the molecule will go straight. Finally, if both electrons are spin -1/2, the molecule will go down in a  Stern-Gerlach experiment.
