private static readonly List<string> _usernamesList = new List<string>();
        private static Object _lockObject = new object();
        private static Random _rand;

        public static string RandomUsername()
        {
            Random rand = new Random();
            int y = rand.Next(9999);

            lock (_lockObject)
            {
                if (_usernamesList.Count > 0) //usernames left
                {
                    string cusername = _usernamesList[0];
                    _usernamesList.Remove(cusername);
                    return string.Format("{0}{1}", cusername, y);
                }
                else
                {
                    using (var wc = new WebClient())
                    {
                        string response = wc.DownloadString("http://www.spinxo.com/");
                        var matches = Regex.Matches(response, @"(?<=' name=""lnkName"">\r\n\s+)(\S.*?)(?=</a></li>\r\n\s+<li><a rel=""nofollow"")");
                        foreach (Match match in matches)
                        {
                            _usernamesList.Add(match.ToString());
                        }
                    }
                    return RandomUsername();
                }
            }
        }