The example texts that you are referring to is called watermark.
Watermark can be used even when there is a label corresponding to input text box. This is a kind of guideline for the user on the kind / type of input the system expects in the input box.
Watermark has to go when the user starts typing but not onfocus. This will help the user in knowing / memorizing the type of data he is supposed to enter till he starts typing. Sometimes it may be that user is not really ready with the data that he is going to key in as he visits the input box. But the moment he starts typing, he is more likely ready with the data he is going to key in.
Following are some links that refer this kind of hint text as watermark:
Following are some examples from famous sites having watermark not cleared on focus but on user starts typing:
- Signup Details screen in Facebook: