If you are really interested in making a run at burning down your server in Vietnam, check out this list.
Chat rooms are practically instant death to a shared hosting account. In fact many, if not most, Web hosts strictly forbid running chat rooms on their servers. The reason is because the connection is constant. Every user is constantly connected to the server and sending/receiving information. Even just a few visitors in a single chatroom can sink an unprepared server. Imagine having every visitor on your site refreshing a page every one to five seconds – that is very close to what a chatroom is like for a server and it is easy to see how it can quickly add a lot of load to your account.
Solution: Don’t do it. It’s probably against your terms of service and, without a powerful server, it is suicide. Instead, use an embeddable chat room, such as TinyChat, as they take the load off of you and are usually better quality self-hosted solutions.
Shopping carts, blogs and CMS applications can all be taxing, but they are all also one-way. The site owner posts material to the site, others read it. Other than comments, users don’t write much to the server VN and there is not too much activity at any one time.
Forums, however, are two-way streets. Users read forums and write to them almost constantly. This keeps databases very active and, in times of high stress, can send them crashing down.
If you get too many simultaneous users on your forum at the same time, you will likely be forced to upgrade your hosting just to keep up with the demand. Sharing hosting and even grid hosting accounts will likely buckle under the weight.
Solutions: You can use a lighter message board system, like bbPress but that only helps some. Your best bet, usually is to just use caching, if available, and make sure that you have a server powerful enough to host your forum. Also, you can try using a hosted forum, like Proboards, which are designed to handle the load.
Full CMS applications
Though content management systems like Drupal and Joomla certainly have their place, they can put quite a tax on a shared hosting account too.
The reason is that these sites have a lot of elements including forums, polls, download sections and other elements that require more work from the Vietnam server, even if they are not being widely used. Templates for these sites tend to be much more complicated and all of the extra elements translate to more weight being put on the server.
Though many are able to run these systems on smaller shared accounts, it is something of a risk, especially as traffic begins to pick up.
Solutions: If you are running a blog or a blog-driven Web site, you will probably do better with WordPress. Not only is it lighter but hosts are more familiar with it. If you must use Drupal or another full-fledged CMS, disable features you are not using and take advantage of their caching ability to try and lighten the burden.