Do you have a data quality process for your Marketo DB? Is it systematic or one-off? Do you apply it before any leads enter system or when they are in system? What type of routines do you have? Junk filter? Duplicate eraser? Field standardization? Field auto-populing?
I've tried to follow a data quality routines but find it very difficult to stick to consistently because other seemingly higher priority tasks take over instead. So I end up dealing with data quality issues only when it really becomes a problem.