Here are a few links to some articles on how to setup security on social media sites such as Facebook and Twitter.
Keep in mind there is a fine balance between promoting yourself and your site and leaving it too open so that others can learn more about you than you want them to.
MSN Article about setting Facebook and Twitter privacy settings
Mashable.com article about the gray area of privacy and social media
HealthLeadersMedia.com article about the patient privacy minefield created by social media
As far as security goes, I’ve always had a beef with 3rd party apps for Twitter that don’t use OAUTH
Essentially, if a Twitter app asks for your username/password, without going to Twitter directly, there is the possibility that the 3rd party app could use it for malicious purposes…
The link for my website goes to a more in depth discussion on 3rd party apps, but the general rule is that if you don’t trust em, then don’t give it to them.