There are two primary reasons why people tag:
They want to find something of value at a later point in time.
They want to share a resource or object with others.
In both cases, navigation plays an important role. To help understand this, consider three distinct activities in the tagging process:
Using and managing your own tags
Using other people's tags
Aspects of navigation involved in each of these steps are discussed in more detail in the following sections.
How tags are created affects whether people can navigate them later. In creating tags, you need to consider such things as access to the tagging service, how suggestions for tags can be made, and the form in which tags can be entered. In general, you want to encourage tagging and lower barriers to creating tags where possible.
People like to have their things organized, but at the same time they can be lazy when it comes to doing it. For social classification to be effective, the act of tagging has to be simple. The process of adding tags should be easy enough to overcome any lack of motivation to tag. Flickr, for instance, allows members to tag multiple photos at once while uploading them (Figure 12-1). Requiring users to tag each photo individually is a good way to ensure that few people will bother. Although bulk tagging means that individual objects in the batch end up with more generic tags, the trade-off of convenience for accuracy usually pays off ...