Purpose of the Dashboard front page
I find the stats provided on the dashboards front page to be totally meaningless. It only shows 12 months worth of data. Yes you can shuffle around the dates but 12 months is all that you'll be able to display.
It's a pity the graph function couldn't be more explicit but I can see why they've kept it to 12 months because any greater than that and the graph data will just look a little bit silly.
Maybe I'm a bit spoilt because I've worked with business intelligence tools and you can do a bunch of cool stuff with graphing tools but this is a forum system so I understand. Just sayin'..