Ah yes, that's true, they in fact were hosted there at some point. I couldn't have picked a worse example :) Or; in a way it is proof that IBM is a bad choice for companies that operate at scale and are low margin and data heavy. Hosting costs must have been a substantial fraction of operating costs for Whatsapp (obviously, long after personnel).
If IBM had even just kept pace and stayed behind AWS with Softlayer after they acquired them, they would have a healthy cloud business by now. It might be because I maintained a system on Softlayer both pre and post acquisition - so I was really close and able to see what was happening - but they squandered a huge opportunity there.