Nervous
There are billions of naked people pictures on the net. That reduces the chance of someone you know finding your pictures, unless you help them by telling them you are a member of TN ;-) Also consider your position in society / work. If you work with children, politician, judge, ect... Having your pictures found would be detrimental. If your just an average guy, construction worker, sales clerk, ect.. It should not be a big deal if found.
And you can restrict your photos to friends only.
From what I have seen, it seems to me that those who do that get an awful lot of friend requests, I assume just to see the pictures. And be aware that this site is targeted by spammers, scammers and prostitutes offering sex (hookups). Mostly blank profiles, weblinks and phone number in them are good indicators that they should be flagged and blocked.