In my experience I would have to say that every time my cat urinated on objects in my home it has been because she was mad or stressed with something. I have a 17 year old cat that used to pee on my boyfriends coat or shoes or anything that she could find of his laying around. She would never touch my stuff. She would be so bold as to look right at me and urinate on his coat and walk away as if to say "there I showed him".
I would take note of any changes that have been made in your life. ie- did you move?, did you get another pet? did you move in with someone? Did you change litter or food?
Cindy made a very good point about the infection though. I would go to a vet first and see, if nothing is wrong with your cat then it might be stress! Good luck.
"The question is not, can they reason? Nor, can they talk? But, can they suffer?"