Free Trials
They tend to release them for specific weekends. Why? I dunno.
If they live near you, why not invite them to your house and let them try one of your characters?
It is what I do.
I agree that trial systems could indeed be permanent, with some possible restrictions:
.1 – Could only be played until level 15 in PvE, or (rank5???) in sPvP.
.2 – Could only choose a low-medium server or low tiered WvW servers to avoid spies in the game (therefore not allowing the exploit of the system) and in the same place increasing the server players playing them.
.3 – Referal system. If you refer a friend, if they upgrade to full account, they receive a ticket to choose server (can choose the same), and the friend receives n*100 gems (where n is a integer = or > than 1 defined by ANet).
There are so many possiblities that i dunno why a system like this is not running already…
/cheers