do more domains pointing to one site help?

[amSportsTalk]

I own four domains I point to the main domain.
main; www.amsportstalk.com
I point these;
www.majorsportstalk.com
www.worldwidesportsfourm.com
www.amsportsforum.com

does this hurt me in pr?
is this good or bad idea to have these names pointing to this one site?
thanks

[amSportsTalk]

any help??