SSL - should I just make my entire site secured?

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http://serverfault.com – I'm planning on building an application wherein my users can create accounts on it, email other users, etc. The site will also have forums, chat, etc. It will also need to process credit cards. I'm trying to decide which parts of the site should be in https. Now I'm wondering if there are any problems with just having the entire site under SSL. Any suggestions? (HowTos)