With 2005 and 2008, they aren't necessarily required for auditing. Actually you could argue that Profiler/trace means they weren't needed previously either. They do many auditing easier in many cases, but they aren't needed.

I rarely use triggers. It's too easy to think that something ALWAYS needs to happen when it mostly needs to happen. I think that you should use triggers when you absolutely need to make sure some data modification needs to force an action INSIDE the transaction. When you can't be sure an application will do this.

Sending emails, alerting, other things aren't necessarily the items for triggers. Business logic not usually unless it's core to the data, not the process.