It's plenty likely. I lost three one day during a heat wave because it got up to 120 degrees in the PC room (poor kid with no AC back then) and I forgot to turn the computer off when I went to work. They all overheated and went belly up. Lost one recently because it was an external and some jackass dropped a magnet on it. And those were just the ones that were *MY* fault.
Modern hard drives are great and reliable, but only once you get past 24 months of useage - that's when most of them fail, because that's when any manufacturing defects or damage due to dropping, shaking in shipping, etc show themselves. I still have a functional hard drive that I had in use for 8 years. I don't have a system old enough to run it anymore, but it still works and has all my sweet Windoze 95 stuff on it.
But at the same time, I've lost 3 drives inside the first year of life for no fault on my part - maybe the UPS guy stepped on it, or someone at the factory was hung over or something, but it sure happens.
In the data center I work at, we've have an average of a little over 3 hard disk failures a month for the past 18 months, just because they've worn out from age, or... just because there was a defect (free brand new warranty replacement, w00t). We've even had a few cases where we got an entire *LOT* of bad drives - ordered a drive array and 8 the 8 drives to go with it at the same time, and several months into their service, they started failing out one by one. If we'd used RAID 0, we'd have been totally screwed every time any one of those drives died.
It does happen, and a lot more than you think, especially if you're like the average computer owner and only have two or three drives in service at one time.
Whatever the OP decides is his choice, but he's going to get a very small performance gain here, since he's not running a server environment, and he's got the chance of losing all his data if either drive goes bad.