Del.icio.us users who bookmark helpful/timely links with meaningful tags (as evidenced by others subsequently doing the same) are rewarded with free advertising, influence on search rankings, and recognition as experts. TopTaggers uses only the last 30 da
Although "tagging" is often promented as an alternative to organization by a hierarchy of categories, more and more online resources seem to use a hybrid system, where items are organized into broad categories, with finer classification distinctions being