Black Hole

May contain traces of nut
Would somebody in the know please comment on any down-sides to registering with Facebook & Twitter, and whether it is possible or pointless to just lurk anonymously?

It seems to me they are being used as a communications medium for things that might otherwise have been put on a small company web page or RSS feed, and I need to at least have a login so I can receive the news feed from individuals/organisations I have an interest in.
I am not really 'well up' on this and can only speak of my usage of Twitter, as I don't have a Facebook account. However I, like you, felt I could be missing out on something useful! I registered for Twitter, not using my real name of course and also using a 'throwaway email address' just it case things went wrong!

I don't 'Tweet' (bird seed is soooo expensive these days!), but I do follow. For example, I follow af123's tweets telling me of updates to custom packages for my Hummy.

I have had some 'weird' people 'following' me, not many, but you can block them anyway.

If it all goes t!ts up, I can just pull the plug and move on....

I only ever post messages on Twitter for technical things like announcing new packages as they are published (and that's automated) but I've actually added a couple of other feeds to follow and it's another way of reading a news feed. MarsCuriosity was the last thing I followed and that should get much more interesting in August.

I signed up for Facebook using dummy details. I need to understand this stuff for my day job although I wouldn't dream of using it. Somehow, though, it has started showing me pictures of people I really know and asking me if I want to 'connect' to them. Whatever its mining techniques are, they are effective.
Facebook is fine for lurking. You have to accept anyone trying to add you so its fairly safe.
I've been on it for years although my usage has dropped its useful for finding information or connecting with friends that you've lost touch with. As long as you set your privacy settings right and disable the email notifications for everything, its fine.

Twitter is a different kettle of fish. I dont use it to tweet per say, I use it as af123 says above, as a sort of news reader.
Again, its fine to lurk, just check your privacy settings.

And if you dont like it, you can always delete your account.
Yep FB lurking is OK but the thing to remember is that all the notifications and 'publicness' settings seem to be all on by default so once you've registered go into the Account/Profile/Privacy stuff and turn things off. I haven't found any practical use for it either but like others on here I need to try and understand it as it comes up at work sometimes. (Also I'm trying to get to know it before my 4 and 2 1/2 year old kids disappear into it!!)