At Gluecon on Wednesday, Mark Suster said that Force.com & AppExchange are mostly about lock-in. I think that's pretty much an exact quote. I tweeted it and expected to see someone react. No one did--at least on Twitter. But I did have a few people mention it to me with some questions about what Mark meant. The truth is, I don't know and I can't speak for Mark.
Any platform provides some degree of lock-in. APIs lock a developer into a particular interaction mode. When I use Flickr's API, I make decisions that lock me into that platform. I can support others, but each is a certain amount of work and the switching costs can be quite high depending on the depth of the API. Similarly, when I build an app for Facebook, it only works there. I can architect things so that I can redeploy on other platforms, but that's work that locks me in.
At the other end of the spectrum are IaaS plays like AppEngine, Amazon Web Services, and Heroku. To varying degrees, each of these causes some lock-in. Heroku is probably the most general. The Rails code I run there can be pretty much run in any other Rails environment, although I have to live within some constraints to run on Heroku. Sure AWS is just Linux on EC2, but as soon as I use S3, SimpleDB or something else, I've locked myself in. Similarly AppEngine and BigTable.
Given this I'm not quite sure why Mark would single out Salesforce. True, Force.com is largely about building apps that work with Salesforce data and if I've invested time to build an app on Force.com or gotten used to the features of one I bought, it is harder for me to switch, but heck, that's true of almost any platform. I'm pretty hevily invested in OS X at this point, but to say that because of that OS X's ability to run applications is mostly about lock-in would be a stretch. It's part and parcel of providing value.
To say that something is "mostly about lock-in" implies that it provides little other value because lock-in is the quid pro quo we pay on most platforms for the value they provide. The fact that SF's customers buy apps to enhance their experience leads me to believe that they're seeing value and that belies Mark's comment by my reasoning.
So, maybe Mark will write a blog post giving us his thoughts about platforms. Until then, I'm not sure I see the logic.