Jacey, not sure we can add anything to what is already very sensible info and advice here.
There is a lot of debate generally at the moment about whether anonymity is a good thing on the internet. Mark Zuckerberg, for example, thinks it encourages people to say things they would never say to people's faces. We happen to think anonymity is useful in contexts like this, because people can say things on GN that they might not be able to say "as themselves" and find support.
Some gransnetters are happy to post photographs and be relatively "out"; others prefer to keep their profiles general (live in Aberdeen, two grandchildren) or not post profiles at all. It largely depends how you want to use Gransnet.
But there is absolutely no reason for anyone to link your username to you - even if it comes up on Google - if you don't want them to.
Personally, I think there's a debate to be had about what attitude we will all have to take in the future to the image that's presented of us on the internet. A friend of mine has just had a Wikipedia entry made about her and she doesn't like the exposure that she can't control. I found myself telling her that she had to accept that it didn't affect her offline identity. But it's very hard to make that distinction - it messes with the heads of celebs, after all, and now it's possible for any of us.
But that's another story. It's as well to remember that these forums are public, but also that they can be completely anonymous.