(I'm used to using the agile features of Jira if you haven't already noticed)
Anyway, AWS provides a few different services that all look promising as appenders in Log4j. The first one that comes to mind is DynamoDB as a good example. There's also another NoSQL serviced called SimpleDB which is rather similar (even has a use case of storing logs), but that's also still in beta and whatnot.
I've begun work on implementing a NoSQL plugin for DynamoDB. My main concern is that all database objects are written as strings. Now this shouldn't be that big an issue with the NoSQL appender as is considering all the data that's written tends to be a string or convertible to a string. I have to explore the API options a bit more to find any better solutions, but there is a sort of JAXB-like marshaller (using Jackson for JSON, naturally) that is useful for giving an attribute value a more complex object rather than relying on foreign keys in a NoSQL setting.