Many "hosts" are clueless when it comes to hackers. They fix the obvious stuff, change a few passwords, and away they go. They don't check for things like hidden directories, CHMODed cgi directories, and other back door methods that can be used to get in.
Many hosts also don't investigate to find out HOW they go in, they just repair the damage and leave the back door sitting off it's hinges, which means as soon as the paint is dry, the hackers come back in and destroy your house again.
I was hacked ONCE, maybe 6 years ago. Within hours, we tracked the hack down to a school in New York State, and within 24 hours, the little bastard was sitting looking at two NY state troopers.
A few months later he enjoyed a day in court.
Alex