I started off playing this with my son when he got his first stuffed animal. I didn't have an animal then and could still play games with him and shop with him in the stores that only require coins that you earn. As he got more comfortable with it, he could do it on his own and has a lot of fun. It helps to be able to read, or else the parent will need to be there with the child all the time.
The characters can talk to each other, and now it's VERY safe because they have a menu to choose from. There are characters who have a blue hat who are "Jr. Cybear Guides" and they can help a newbie navigate the site.
They keep adding new features to it, such as beach front homes .... It definately is tied in to merchandise - the more you buy at the real store the more you can convert them to speacial bear bills there to buy exclusive items. However, it still is a lot of fun without ANY purchase. That makes this site unique to others like webkins ... A companion site is bearvilleinsider* this will give you tips and secrets.
I find this site enjoyable even as an adult. There are lots of games and activities. The only concerns I have are with the commercialism aspect. As an adult with a rather sizable BABW collection compared to most people (I have a total of 11 friends in the house with 10 of them registered on the site) plus lots of clothes, I have the option of spending money in the store and receiving the currency generated by my purchases. I am constantly approached for trades by younger members who think I should just give them items for nothing.
I think that kids will get more out of it when they are older than 7. They really need to be able to read and be confident in navigating the site. I found that my kids would much rather go play on the WebKinz site than the BuildaBear one.