I learned my lesson about renter's insurance a few years ago.
The apartment I was sharing with my roommate was covered under his parent's policy (well, technically only his stuff was, but the only things of value I had were the TV and the computer, so I "gave" them to him when we moved in) because he was still in school. The coverage expired in mid-May when he graduated, but we were moving out in mid-June, so both of us figured it wasn't worth the hassle or the money to get insurance for one month.
The the power company had problems in the neighborhood, and we had wild voltage spikes and fluctuations for a few days. It killed the microwave, a TV, a VCR, several components of my PC (cpu, power supply, and a hard drive), and several other appliances (along with 5 of the 8 A/C units in the apt. building). Unfortunately, the power company is not responsible for any kind of damage, so we were SOL.