The other day I followed a link on one email I received that took me to a set of products by a company (to remain unnamed here, because I prefer philosophical discussions and not trashing specific companies). I was just curious of what they had, read their offerings and closed the browser window. Nothing really surprising here.
What surprised me was that in the next day I receive an email from somebody at this company saying that they know that I've accessed their website looking at product X and if I had any question, I could contact this person.
I am very well aware that it's easy to track specific customers to know where they went on your site. It's even easier if you send them an email and they click a link on the email to go to the site. It's also very helpful to do that, so that I know how well your campaigns are working and how "real" each customer is. But using this information to personally contact the customer saying "I know what you did yesterday!" is probably going too far.
On one side, it shows you are interested. It tries to put that human touch you'd receive in a store: when you are walking around a set of products, it's common for a sales person to come around and ask if you have any questions on those products. That's the connection they are probably trying to accomplish with that email.
However, connections on the internet are psychologically very different from those in a physical store. It requires less commitment to visit a website than to enter a store, so it's more common for people to be just browsing on a website than on a store. And it's very annoying to get a sales person come to you asking if you need help when you are just browsing.
So my suggestion is: yes, use the great ability that the internet provides you to track your clients so that you can better understand how you can make their lives easier (for example, if they all go through 5 clicks to know your shipping policy, then make it easier for them to find it; if every time they look for product X they end up clicking around to get to product Y, provide them with a direct link).
However, if you want to make a personal connection with the customers, understand the context of the customer first. Remember that you can't see his face, you don't know if he is trying to make eye contact, or trying to avoid eye contact. Be aware of that, and you will keep them coming back. Be unaware of it, and they will stop clicking on your links (like me).