Not sure about 'Infinit!' maybe lisa or another SBI'er could enlighten you. Most of us when talking about our own hosted blog were on about WordPress.
http://www.wordpress.com (host it on there server)
http://www.wordpress.org (download it and host it on your own)
You will need to download the files from the second link, and upload to a sub folder in your SBI! FTP.
It basically just gives you so much more freedom providing you with lots of features a huge plug-in section and control panel its truly great.
http://codex.wordpress.org/About_WordPress
You backup your database which is requirement for installing Wordpress so you will not be able to use SBI! to host your blog unfortunately I think there working on it, when they do that's my key to join
Backing up your database simply saves all your comments posts, user information. Also you mentioned Web 2.0 (my space) As i know of you cannot backup your profile account, they have complete control and when you signed up for it you will have probably signed there Terms and Conditions and in that big block of writing somewhere will be:
"We have complete control of your account and we may delete it if we feel necessary."