Maybe a stupidly obvious question?

The 2 options when a user signs up:

'Gimmie a blog..'
'Just an account...'

Is there a way NOT to show these and have the default as either? For example, on one site I may be running a blog network, in that case, they will want blogs (sites) and NEVER just accounts.

The other side is BuddyPress, where users just want accounts and not sites - of course this could be run in a non-network set up but I'd like the option.

Also, how do you re-name the text on these without core hacks? Sure, the word 'gimmie' is cool, but not really for every type of site.