Scaling UP is never an issue with IBM's core technologies like WebSphere, DB2, etc. as long as you have or can find the technical resources to implement it.
Where IBM seems to fail is scaling DOWN for smaller organizations. Connections 5.0 on-premises would have required us to create 7 servers -- yes, they would be virtualized, but still that's 7 OS licenses, 40 virtual CPU cores, 80GB RAM, and a few TB of hard disk space. All to replace Quick which runs on 1 server with 1 OS license, 4 cores, 8GB RAM and 600GB of disk. Granted, there are major differences in capabilities between the two, but how do you get a CFO understand why features like a mobile app, file sync, and social sharing require 10x the back-end resources?