While these are fairly obvious they are something that users pushing HTML5 should be aware of. The first is vulnerability. What does this mean?
The next issue is security. Apparently the standards have not really been developed with security in mind as it will really be up the developers, users, and browsers. So there are going to be some issues when this is used more often…and of course this is the case with any new technology. Here is an article that goes into the topic: