Winter '12 Force.com Platform Release
ReadOnly Annotation - Generally Available
The @ReadOnly annotation was previously released as a pilot in Spring '11 and is now generally available in Winter '12.
The @ReadOnly annotation allows you to perform unrestricted queries against the Force.com database. All other limits still apply. It's important to note that this annotation, while removing the limit of the number of returned rows for a request, blocks you from performing any DML operations within the request.
The @ReadOnly annotation is only available for Web services and the Schedulable interface.