Always brace cakes!
ABC! While you don't always have to brace cakes, you need to check each type of cake and make sure it is stable. Most 500g will a large enough base that it won't be an issue, but you have to be careful with 200g. Usually putting a spent cake on either side will be plenty, or using tape or glue if on a board. Everyone should already know this, I was just thinking about it again because yesterday I was poking around the Red Rhino site and watched their demo video. I'm not trying to say anything bad about them here, just pointing out that accidents happen and safety is important.
Here is a little clip from that video.
Addendum: The first review of Power Play is relevant to this post and made me laugh.