Question : GLobal Catalog and Infrastucture Master

In many articles, it says that Global Catalog can't have an Infrastructure Master role.
I would like to know how they impact each other.
if it's recommended  not to have GC and IM together, Why it doesn;t prevent you from giving a role of IM to a GC or make an IM a GC?

Thanks

Answer : GLobal Catalog and Infrastucture Master

well this might clear it up for you

http://msmvps.com/blogs/ulfbsimonweidner/archive/2005/03/08/37975.aspx

as for why it is allowed ...it might be because if you have a single domain configuration and you are not linked to other domains then there might not be a problem with have both these roles in a single system