there are only three manufacturers of drive mechanisms left in the world: seagate/maxtor, western digital, and ibm/hitachi. after that, you are just talking about whose case the drive mechanism is mounted in. seagate and maxtor announced their merger in late december. and yes, the enclosures can fail... but that rarely leads to data loss, compared to the drive itself crashing.
everyone has a story of how SOME drive has failed... undoubtedly from every manufacturer. i am currently using drives from all 3 which have been in service for a long time and continue to function well. however, they will all eventually fail. ALL DRIVES FAIL. they are electromechanical units that cannot last forever. expecting otherwise is like expecting your car to run forever. anecdotal evidence in the past has suggested that of the IDE drives, seagate's barracudas were particularly reliable. they certainly maintained the longest warranty when everyone was shortening theirs. that may change with the merger.
personally, i have been buying drives for a couple of years from an online retailer--coolerexpress.com. i've found which enclosure seems to be reliable and relatively quiet (the bytecc plastic 3.5" model) and i have them put a seagate in it. currently a 160GB firewire unit sells for $114 plus tax and shipping. i will keep using these until i start having trouble with them.
the bottom line, as always, is to back up religiously.