What are the pros and cons of goverment regulation of businesses in the US?

Honestly, I’m quite ignorant of the nature of goverment regulation on businesses here in the US, so I would be grateful if through Fluther I would get some enlightenment on its pros and cons.

I’ve been hearing and reading that regulations are harmful to the present economic situation. Does this mean it was helpful before? Would anyone even bother to regulate anything for no good reason?

Is there really a bad guy vs good guy scenario in this argument and is this really a battle between evil and good, regulations being “evil” as one political party seems to paint it while the other side touts its critical importance?