Once you start having a lot of websites, you need to be able to track which one of them are getting traffic and from which keywords, also you need to make sure your sites are up and running everyday so you need to have a tracking system that shows a dashboard for all your sites at the same time so you can see in 5 minutes that all your sites are up.
Google Analytics does that but it also links all your sites together to any other internet marketer and it allows Google to know that all your sites are linked together and it gives them a lot of information on your websites, which is what you don’t want in case they decide you’re doing something they don’t like and ban you.
It doesn’t link your sites together and it has a main dashboard. It’s not self hosted which means no time wasted troubleshooting.
The only downside is if you want to save data information about more than the last 500 visits per website, you need to pay. Well personnally I only need that for a few websites so I pay and it’s very cheap.
If you want to save data for your website for a long time you should use Woopra.com as well. It doesn’t link your sites together. It doesn’t have a main dashboard though so I suggest that you use both.