I had one FoodSaver bag fail along a factory seam, I'm pretty sure it did, anyhow, but the other failures have been because of a poor seal that I was responsible for. Like Cliff, I do a lot of double-sealing.
(Of course, some of the incomplete seals could be because I'm using an aging, superseded model that cost $58 new.)
Weber Smokey Mountain -- "Want authentic smokehouse flavor?"
22.5 Inch One-Touch -- "The legendary Weber kettle"
18.5 Inch Original (R.I.P.; garage mishap) -- 10 books S&H Green Stamps, 1968
Weber Performer -- Craigslist 2007