In some locales sitting on the street writing down a list of people coming and going is legal, but leaving a camera pointed at the street isn't. Legislation like that makes a distinction between an action by a person (which has bounds on scalability) and mechanized actions (that do not).
Fair Use is the relevant protection and is not specific to manual creation. Traditional algorithms (e.g: the snippets, caching, and thumbnailing done by search engines) are already covered by it.
