Agreed that data sizes would have been far more of a challenge – far more people used clustered services just because a single box only supported so much RAM, RAID arrays for IOPs and size as well as redundancy, etc. – so it's arguably become much easier for a growing chunk of the industry.
I'm not sure you could get 1TB of memory and multi TB SSD drives anywhere in the 2000's, even for a million dollar. That makes a major difference in the ability to scale up. Data didn't grow, storing 1M user account always took the same space.