TB (as well PS) is saving allot of statistics information that increase the DB size allot.
Usually I truncate those tables manually to reduce DB size.
So I think we should have an option in the BO to do that process, either by truncating or deleting rows.
I am talking about:
connections, connectionssource, connectionspage = saves IP address, referrer, etc.... of connection
guest = saves guest information (similar to GA)
page_viewed = well.... you know
pagenotfound = same.......
This is nice info to have but in 99% of websites are useless, plus you have GA/Piwik for all that information and more.
In some cases those tables can reach 100MB-500MB (depend how many years your site in running).
I had one case that I tried to backup a client DB and it ended up in 750MB, after truncating those tables the same DB was only 11MB.
Now, I am no SQL expert but I believe that smaller db will execute faster.