blog automatically added in permalink in main site

Hi,

I never saw this issue before because in MU as well as MultiSite so far I have always coded for the subsites and never for the main installation. I always had a static page for the main installation and thats it. But I am working on a new site now which has MultiSite enabled. Now this main site will have further categories and other sections. When I try to set the permalink for the main site I see that /blog is automatically added to the structure. I am following this structure /%year%/%category%/%postname% but it is becomeing /blog/%year%/%category%/%postname%

Since the permalink starts with a word "blog" wont it hamper the performance in future. Or does the main blog always will have this complication or does it plain just doesnt matter? I really dont want the blog there. Is there any way to avoid it?