The majority of America's pipelines were built decades ago. About 60% of pipes were laid before 1970, and close to 40% were built in 1950 or earlier. There is increasing concern that these old pipes are a major liability, and accidents like ExxonMobil's (NYSE:XOM) oil spill in Arkansas two weeks ago will happen more frequently. In this video, Fool.com contributor Aimee Duffy talks to fellow contributor Tyler Crowe about two other factors that could affect the integrity of our aging pipes.