As a techie and owner of a geek-squad style company, I find that the worst thing for a computer is an incompitent user. A person that clicks on ads, downloads from advertisements, has no anti-spyware or firewall, incompitent overclockers, etc. Most people just screw up thier own computers. Notice how the educated(in computers) people never have problems. 90% of my clients create thier own problems and its almost always preventable by getting some computer common sense.
Hoarding photos on your phone?
Those picture are hogging memory and could be slowing down your phone.