ASP.NET Cookieless sessions and JQuery AJAX

I was trying to get some jquery ajax calls to work after converting a site to cookie-less sessions (don't ask). I noticed the following code wouldn't work:

$.post("/bin/getsomedata.dll", {'id': id},
   function(data)
   {
       doSomething(data);
   }
);

I changed it to:

$.post("<%=Response.ApplyAppPathModifier("/bin/getsomedata.dll")%>", {'id': id},
   function(data)
   {
       doSomething(data);
   }
);

and all was groovy

I also noticed that when I turn off cookieless sessions, everything still works. It appears that Response.ApplyAppPathModifier() only alters the URL when I am in cookieless sessions