* Blob Leases allow you to claim ownership to a Blob. Once you have the lease you can then update the Blob or delete the Blob without worrying about another process changing it underneath you. When a Blob is leased, other processes can still read it, but any attempt to update it will fail. You can update Blobs without taking a lease first, but you do run the chance of another process also attempting to modify it at the same time.
* You can opt to use either optimistic or pessimistic concurrency models to manage access to blobs and containers in the blob service.
References: http://justazure.com/azure-blob-storage-part-8-blob-leases/
http://www.azurefromthetrenches.com/?p=1371