MKTO Web Personalization allows you to show customized content for different targets. For example, show a specific web banner when country is U.K. and Job Title is Marketing Manager. However, I'm not sure where do these values (U.K., Job Title) come from. Is it from MKTO? I'm asking this question because if you have some dirty data in your MKTO instance this segmentation would be difficult (for e.g. if Job Title or Country happened to be a string for some reason). Would you have to ensure all your data is clean before using Web Personalization?
I no longer use this module, but when I did the data came from your Marketo database connected to their record. If you have bad data, then yes I'd expect you'd run into some issues with your customization.