Some aren't as good as they used to be
LaCie does make some great drives. I have one myself. My boyfriend, a filmmaker, has a ton of them actively in use. It's really creepy when he fires up his editing rig and they all wake up at once. A faint humming sound, the air feels kind of energized - like in sci-fi movies when a portal is about to open up.
I have heard of a few problems but it seems the worst problem is dealing with the people at LaCie in the rare instances when something does goes wrong.
Another problem with enclosures is proper cooling and ventilation.
You know how some online retailers have "people who bought this also bought" like on Amazon? I've seen evidence of a lot of people buying a really good drive with a really cheap enclosure. Then later, they give the hard drive a bad review. Go figure. The same is true in reverse. Sadly, when someone combines something expensive with something cheap, the expensive component will usually get blamed for the failure.