This manual activity is popularly known as data mining. It includes such techniques as flipping, x-raying and URL peeling. Recruiters and sourcers use these techniques to pick through the documents stored online and find resumes or contact information. Unfortunately, data mining is even more time-consuming than sorting through the junk retrieved by spiders. They must capture the advantages of automation while avoiding its downsides.
Spiders can dig deeper.
According to a study by the Corporate Leadership Council, manual resume sourcing can only reach top-level pages, which is estimated to include about two billion pages. Spiders are tireless. Sourcers and others who do manual searches basically act as hunters and gatherers. While humans can perform such tasks, they aren't tireless, will not work 24 hours a day, seven days a week, and want to have a life. A resume database is just a bunch of digital documents about digital strangers.