What's the point of Houses?

[greatlit2003]

No: HPFGUIDX 75608

Hello.
I am wondering why Hogwarts needs these different Houses to begin 
with. I mean, what is the point of sorting all the brave students to 
live in a dorm together, all the ambitious people together, etc.? 
What does that accomplish? Everyone receives the same education 
anyway (different Houses have classes together). I understand that 
the students need to be placed in groups for the sake of 
organization, but why does that organization (i.e. Sorting) depend on 
their personality? Why can't the Hat just randomly select students 
for each House? A lot of bad will seems to crop up at Hogwarts in 
large part to the House system. Any thoughts?

greatlit2003