Hello. In my quest to build a site that has blogging capabilities, I am searching a blogging service. Please note that I am not interested in installing something like wordpress in-premise. I am looking for a service which will provide me with APIs to read and write blogs and be responsible for persistence and performance. Needless to say, it should be adequately secure and should be scalable. Any pointers will be appreciated.
WordPress (and almost all other blogging sites) have what is called a MetaWeblog API built in. Dozens of applications out there are written to use it. Such as Windows Live Writer (my favorite).
Even Microsoft Word has built-in support for the Metablog API calls (File -> Post to Weblog).
Now, if you want a service to truly host your entire blog backend, while you write a frontend (aggregate listings, pagings, searching, etc), you'll be hard pressed to find an inexpensive service to support that. Many applications have been created for that purpose, with a hefty price tag.
Pretty much every blogging package supports the MetaWeblog API or some alternative. If you are happy with whatever services a particular hosted provider has (WordPress hosting companies exist, for example), then your app or your users' favorite blogging tool can call the metaweblog api and you're done. Movable Type also has a similar API.
Edited to add: I'm slightly behind the times because I just learned about it, but AtomPub is making pretty good headway in the blogging API mindshare battle.
If what you actually want is an api to support blog provisioning, I am less certain of your options, but I suspect that many hosted services would be willing to expose something if you provided enough financial incentive.