Assume for a moment you have 10 000 employees and 10 years worth of business correspondence in Gmail, Outook.com or similar. Now for email, there is usually at

Assume for a moment you have 10 000 employees and 10 years worth of business correspondence in Gmail, Outook.com or similar. Now for email, there is usually at least one or two open apis for getting that data (pop/imap) - but even so, migration is a costly affair. You could move all new correspondence to a new (eg: on premises) system - but you'd have to keep paying to retain the same access to your business history. Take any of the many business/crm-apps, where there's no clear migration path (you'd want both history and business process rules) - and it's easy to see how SaaS might easily facilitate "rent extraction"? As others have mentioned the problem isn't unique to SaaS - but with an on premise solution, you might be able to move some terabytes of data by simply moving some physical drives - or at least have local access via you SAN. With a cloud provider, many businesses would struggle to get at the data at a higher rate than 100mbps even with the help of the SaaS provider. And there's often no option to keep access to "old" system/data without paying rent, unlike some on premise solution (keep the old system, on it's own network segment, ticking along for historical records (or: in a VM).