One particular web app which isn't that great is IRC web chat. Most IRC servers are keen on users connecting from their real connection, as it's hard to track abuse when connections are being proxied by a web server. Using AJAX or JSON with a web server isn't that ideal either, browsers have to constantly poll and refresh with the server to receive the data, this typically requires a light weight web server as Apache with PHP or Perl is hardly efficient for multiple users. The most common approaches over the years has been CGI:IRC, but this is just yet another inefficient Perl script which keeps the connection open. One of the oldest methods is using a hefty Java application, hardly friendly for users.