first, lawrence and ingrate are correct, this is really too vague, but since it's been 4 months, i will just jump.
a. good idea--makes concrete many of the vagaries of modern theory (an over-reliance on the magic of so-called community, for example). can encourage life skills that will serve people well (getting along, conflict work, relying on themselves and each other instead of anonymous outsiders). building interdependence. can be a strong defensible place to protect against attack. can be an example of how things could work differently for many more people.
b. bad idea--can mean absolutely nothing in terms of people's goals for themselves (arguably frat houses are a kind of commune, for example). can create insularity and stagnant relationships. can reinforce people's messed up beliefs, make it harder for people to find what they would rather be (thinking at the moment of people trapped in religious communes, although i have only media stories to refer to for that, so perhaps bullshit; premise still seems viable though). could be an example of how no matter how the form changes, the result continues to be co-optable by the status quo.
obviously many of the good things are also bad things, given one's perspective.