There might be issues with Bigfoot-like drives with platter stability at the edges, but I have no idea if this is actually the case. What I do know is you get better performance towards the edge of the platters, and for larger drives, the variability in throughput might be a downside for some buyers. Seeks times are also slower.
There was a variant of the WD Raptor that took the opposite approach: it put a 2.5" 10k RPM drive in a 3.5" enclosure, but this drive played the role SSDs do today; they weren't for mass storage.
There was a variant of the WD Raptor that took the opposite approach: it put a 2.5" 10k RPM drive in a 3.5" enclosure, but this drive played the role SSDs do today; they weren't for mass storage.