In a lot of APIs I've dealt with, you can create resources with ids that match your own resources, hence wanting to use PUT for creation, e.g. if you have users in your application and you want to extend them to this web service, instead of having to store an additional "foreign key" per user, you can just PUT users in the web service with ids from your own service.

I'm doing this for the API I'm building, as modeled on FatSecret's API.