Anytime a child uses the internet safety has to be a concern. Since there is no way to know for sure who you are talking to there is always a small risk. Forums are not necessarily dangerous places for kids but they do have to know how to protect themselves. This is a lesson that they should learn when they are first getting online so that they will be able to stay out of trouble.
Like anything on the internet forums can be safe for kids or they may not be. The vast majority of them will be just fine but there are some that are not. While it is best to keep your kids away from the forums that are not safe for children the most important thing is to teach them how to be safe online. This will allow them to ensure that they are safe no matter where they happen to go since there is a good chance that at some point they will stumble onto a site that is not safe.
In general most forums are safe places; they do not usually allow inappropriate discussions to take place. The one thing that you do have to watch for on a lot of these forums however is internet marketers. They will often go to these sites to promote their products. If your kids have a way to make an online purchase they may well find themselves spending a lot more than they thought they did. This is something that you have to be careful about.
The other likely scenario that your kids will come across on forums are ones that have discussions that are not appropriate for children. In this case you are going to have to control their access to these sites since these are forums that are set up for these types of discussions. It can be difficult to keep kids away from these types of forums but you will have to make an effort. At some point you will also likely have to discuss with them what they have read on these sites to make sure that they don't get the wrong impression.
While real danger on forums is not all that common it does exist. The big worry of course is that somebody will use a forum to lure a child into a meeting. This is something that you have to really teach your children about. You can try to keep them away from forums where this is likely to occur but the reality is that it can happen on any forum. You have to make sure that your kids know that they cannot meet people they have met online in person and that they cannot share any personal information. This will keep them safe no matter where on the internet they happen to go.