Uncontrollable and amateur scraping can really hurt a website. The best option to extract information from the web is through APIs. Nowadays, almost every single service has an API server where you can query and get data, Facebook has the dev.facebook, Twitter also, even Amazon! It is always best to plan and think before going for a massive crawler.
My friend Michael has a very interesting blog! Michael among others he is an API expert, so pay him a visit to explore the world of APIs!