Textarea atual:

<textarea id="event_content">
This text area could be full of information..www.london2012.com
And might contain upto 5 links that all need updating.
www.rio2016.org

Link already converted. this should be left.
<a href="http://www.thetimes.co.uk" target="_blank">www.thetimes.co.uk</a>
</textarea>

Textarea desejada após jquery: todos os links a serem limpos / substituídos por tags e target attr

<textarea id="event_content">
This text area could be full of information
<a href="http://www.london2012.com" target="_blank">www.london2012.com</a>
And might contain upto 5 links that all need updating.
<a href="http://www.rio2016.org" target="_blank">www.rio2016.org</a>

Link already converted. this should be left.
<a href="http://www.thetimes.co.uk" target="_blank">www.thetimes.co.uk</a>
</textarea>

21 de julho de 2012 -Ωmega's código funcionou um tratamento obrigado, mas poderia ser melhorado, deixando links já convertidos?