There isn't any problem having many locale lying in your system. But if you have computer with minimum hard disk space like Dell Mini 9 then it might be good idea for you to remove unnecessary locale and free space. Also you don't have to waste time compiling all the locale when you only need some of them. This saves time while updating and installing some application.
Now to remove the unnecessary locales, open terminal and type
sudo apt-get install localepurge