Is it a good idea to use PollingDuplexHttpBinding with Silverlight in conjunction with the function RegisterScriptableObject to achieve Comet-style javascript f
RegisterScriptableObject
You'll have some serious scalability problems, and it's a royal pain to implement. See:
http://devgripes.wordpress.com/2009/11/14/pollingduplexhttpbinding-absolute-rubbish/
If you want a Bayeux implementation in Silverlight, you want WebSync.
(Disclaimer: I work for Frozen Mountain Software)