If you avoid buying something because once or twice in a million it doesn't work, seems like there would be nothing on the market to buy.
The BLIS in my wife's 2010 MKT works just fine, as it has in at least 30 other Ford vehicles I've driven with it. Unfortunately as with everything mass produced, there are always some that won't work, but that small percentage is no reason to avoid buying something you might otherwise want.
My initial decision to avoid BLIS was because I was familiar with the standard mirror arrangement from owning a Fiesta. Properly adjusted I can have virtually no blind spots so my thought was "why buy this when I can have success with the base setup?" Since then I have toyed with getting it on the next car, and I can cope with it reporting hedges and the like ... but the possibility of the electronic fluff at the wrong time just doesn't sit well with me. These cars are already techno-marvels ... why add more potential for pain?