I understand, and use, the subscription options throughout the site. I don't understand the option to subscribe to a person instead of being friends with him. This is an option I think I'd rather not have. I don't think it feels comfortable to know that someone can follow your doings without being in your friends list- a list you can view and control.
Regarding blogs- there is currently no option to subscribe to an entire blog, but only to single posts, which is a bit ridiculous. So although subscribing to a person might give you the option to "subscribe" to his blog, it also gives you the option to follow him on other areas he might not be aware of. I don't like it.
The option to subscribe to a person- I think I'll hide/remove. other subscriptions- I don't mind having.