I just had my account suspended today for using 21% of resources. I'm still trying to get it turned back on but the provider's terms say they can do this without warning and after talking to Host Gator (considering moving to another provider) it seems Host Gator have the same conditions.
I still don't know what exactly happened. I get about 2000 visits per day between ALL my sites and no sudden movement in traffic or SERPS.
Just a warning for all with shared hosting, you could lose everything in a second without warning.