Loyalty is much more than getting people to return to your site. Loyalty is about a high level of trust and a high emotional involvement - a mix of rational and irrational/ emotion driven elements. Another way of looking at it, is in the context of a friendship.
Usually the basics for starting a friendship is common interests. This is a rational reason. As the friendship progresses there is an emotional involvement, call it love, that binds the friendship together. For any brand, to be at this level of the relationship is key to getting loyalty beyond reason. In my view brands in this category include Amazon, iPod, Toyota, etc. If I wanted to buy a book online, I go to one place... Amazon.
The rational is all about the value/experience that I get from the product/service through interaction. These are things like low price, great online experience, easy to understand functions. Emotion can be influenced by the rational basics, but this is just the start...
In an online environment, where the person at the other end of the mouse has all the power, providing a good online experience is a given to build trust. Emotion is personal. To get into that space you need to have the ability to form a dialogue. Most brands online get this right, to some extent. The dialogue only gets you some level of trust. It is how you use this trust to further the relationship and dialogue that gets you into an emotional space.
Dialogue is not only an e-mail or a phone call. This could be brought through in the way that the site 'instinctively' knows you and your needs, i.e. profiling.
Amazon tries to provide me with items that it thinks I might like, based on my past purchase behaviour. I welcome this, as there is so much out there and it's difficult to find it all. Most of the time I'm not interested as they get it hopelessly wrong.
It would be better if every now and again when I purchase a specific item, they perhaps ask me why I'm interested in that item. If I knew that by providing this info, Amazon would be able to send me information of similar interest, I would do it, as long as they don't spam me with useless info - it's a fine line. I trust Amazon and I'll let them know a lot more about me, if that means that they can look after my interests and needs.
However, past purchase behaviour is not necessarily an indication of future purchase, this is why it's essential to understand the emotional side of loyalty. Understanding your customer's/user's needs and their reason for purchase is essential in building loyalty beyond reason.
Become a friend to your customer and they'll be loyal to you. Just ask the local butcher in a small community.