Are there still reliability problems with high capacity magnetic disk drives?
When 500GB and 1TB drives first appeared on the market, they had significantly lower reliability than their smaller (250GB and less) brethren. I have first hand anecdotal experience, as I bought several 500GB and 1TB drives (< 10 total) over a span of about 2 years (2006-2008) and have had 2 of them fail within 12 months of purchase.
In early 2007, Google released a study of drive failure statistics (http://labs.google.com/papers/disk_failures.pdf) collected from their data centers. This study indicated, during the period of the study, that the high capacity drives had a significantly higher failure rate than the lower capacity drives.