It turns out that the gratis vs libre croud are still obsessed with the desktop - while the industry turns toward the cloud.
CNET asks the Free Software Foundation (FSF):
Instead of soiling your feet in Apple's shrines to proprietary software and hardware (aka "Apple Store"), why don't you instead demand that the web services we use remain open? Why not fight for open data guarantees? Why not, in other words, do something that affects more than my ability to listen to Radiohead on the Zune, and instead affects my ability to take years of email stored in Gmail and move it elsewhere, offline or online?
Service portability will be a big challenge for Cloud Providers. Interoperable APIs are a good start - but open data will be the key to customer satisfaction. Dynamics CRM Online vs Salesforce.com is a great example of this. With SFDC is hard to get your data back (not impossible - but not easy). MSCRM Online gives you your complete database - all your data - not just a collection of CSVs. Then you can take that DB and migrate it to the system of your choosing.
PaaS providers will need to ensure that they can offer platform portability (where feasible) to the partners which build SaaS offerings on top of them. In theory everything could be portable but at some point it will begin to negatively impact COGS.
SaaS providers will need to consider how they want to attract and retain business. The ability to import data from your competitors is a strong selling point (eg. the Salesforce.com migration template isn't in MSCRM just for fun). SaaS providers should take the leap of faith and encourage their customers to take their data whenever they want. Smart SaaS players will make 'ease of leaving' as much as a selling point as 'ease of arriving'. As the old adage says: "If you love something, set it free. If it comes back to you, it's yours. If it doesn't, it never was."