I've been playing around with BlogEngine.NET, and I've hit a snag making it work with Microsoft Azure.
BlogEngine.NET was built to store files inside the application's own file system. So if you install the engine in, say, c:\inetpub\wwwroot\blogEngine, by default the files will be in ~/App_Data/files, which maps to c:\inetpub\wwwroot\blogEngine\App_Data\files. All of the file-handling code, even the abstractions, assume that your files will have some kind of file name that looks like that.
You must never store files locally in an Azure cloud service, because at any moment your virtual machine could blow up and be reconstituted from its image. Boom. There go your files.
You really want to use Azure storage. In its purest form, Azure storage organizes files in containers. A container can't have sub-containers. You access a container by its name only; paths are meaningless.
But because BlogEngine.NET assumes that all file stores use path names (which even works for the database file store plug-in, for reasons I don't want to go into), creating an Azure Storage provider for this thing has been really annoying. I've even had to modify some of the core files because I discovered that it applied a default path to any file request no matter what storage provider you used.
Don't even get me started on the bit of BlogEngine.NET's architecture that pulls all files around through the UI instead of allowing them to live in a CDN...