A picture may be worth a kilo of words, but typing into Google Image the single word "rosebud" returns about 60,000 pictures.
The power of an individual keyword is both good and bad. It can find a virtual stack of Web pages. But it is unable to differentiate between the flower in bloom and legendary film director Orson Welles's scowl. Ideally, an Internet user should be able to use the likeness of a rose to tell a search engine to find others like it.