I would argue that real infrastructure or vendor "lock in" is due to the friction of learning the API's associated with each cloud platform. Obviously, one can choose to use all the services of the cloud platform they will deploy to. However, and in most cases, that is not a strict requirement to use the cloud platform to begin with. "Lock in" seems more like a self-created problem than anything.
And it's not just cloud platforms. Every tool you use becomes more engrained the more you use it.
Put plainly: It seems silly to me how people will shout "vendor lock-in" when using a service like DynamoDB or Kinesis, but will be more than happy to learn how to set up and maintain a Cassandra or Kafka cluster, along with Zookeeper, Puppet/Chef, and all that goes along with it. Those are not insignificant costs!
I get that those aren't vendor-specific, but at some point you're just doing a lot more work, maintenance, and tying yourself down to a stack (and whatever employees became experts in them), and for what benefit? So you'll theoretically be able to move away faster if AWS goes rogue, long after your startup gains traction?
I think those reflexively dismissing cloud services due to vendor lock-in need to take a step back and look at the big picture.
Costs are high for aws. You might be able to pay a little more now but when you need to scale you may find you are priced off of aws.
More importantly, though: you quite possibly won't ever find yourself "priced off of aws." Netflix isn't. Workday isn't. Spotify isn't. Pinterest isn't. Dropbox only transitioned off very recently (reportedly for more control). Some of the biggest players on the web were able to scale and grow beyond most of our wildest dreams without it holding them back, yet still some recommend adding significant man-hours and complexity up-front just on the off-chance it becomes necessary after it's successful?
Let's be realistic here.