Hosting OAuth services is so easy - based on the new ServiceStack API.

FriendsService.cs

using ServiceStack.ServiceInterface;

namespace OAuth.Services
{
    [TwoLegged]
    [ThreeLegged]
    public class Friends : OAuth.Service
    {
        public object Get(DTOs.Friends friends)
        {
            return new DTOs.FriendsResponse
                {
                    Friends = UserRepository.GetFriends(User.UserId)
                };
        }
    }
}

TestController.cs

using System;
using System.Web;
using System.Web.Mvc;

namespace OAuth.Controllers
{
    public class TestController : Controller
    {
        //
        // GET: /Test/

        public string Index()
        {
            var api = new OAuthJsonServiceClient("http://localhost/api/", "CONSUMER_KEY", "CONSUMER_SECRET");
            var users = api.Get<DTOs.FriendsResponse>(new DTOs.Friends(){ Username = "jcarruthers" });
            var ret = "";
            foreach (var user in users.Friends)
            {
                ret += user + ", ";
            }
            ret = ret.Substring(0, ret.Length - 2);
            return ret;
        }
    }
}