This was extensively explained in the blog in great detail, but here I will be simplifying it.
Anyone can be an outlaw, but doing so can effect your characters alignment, and stance on how npcs will interact with you. The most obvious thing here is doing anything thats against the Law such as intimidating people for money, or hurting them, or even breaking and entering homes can have several consequences
Current consequences:
#1 - you can get arrested
#2 - You can pay a hefty fine up to 1000 gold
#3 - NPCs you intimidate or hold up will stop talking to you unless you do something for them (such as paying them or doing something for them)
#4 - You can simply die, this depends on what happens. Many NPCs will be much higher level than the average player so its very likely getting into a scuff with one can lead to some nasty bruises or being un-alive.
There are benefits to these sorts of things such as instant gratification. Rather than risking your life for loot in a dungeon you can do it through various npc's at the risk of getting caught and improving your standing with a guild, knowing that you work for them first. Many guilds don't like vigilantes and neither do the Local Constabulary.
Constables are always on the look out for would-be thieves even if you arent a part of a guild its always a good idea to hide yourself from them with a helmet or hood.