Marketpress Question: I need only some blogs to have marketplace not all

Hello,
I created a muli blog website and installed marketpress plugin. I network activated it. Then I created a marketplace blog which is subdirectory: http://mysoundgrid.com/marketplace and I want it to be my marketplace where users can create stores.
When I created a couple of stores there I noticed that the rest of the blogs where I don't want market place to be installed appear in my store list and have marketplace installed.
I assume that network activate did it for every blog.
Is there any way possible to have a marketplace on my network where some users can have stores and others can just have regular blogs without the stores.
Thanks,
Helen