The phrase "a vast source of information" is correct and usable in written English.
It can be used when describing a large and comprehensive collection of knowledge or data on a particular subject.
Example: "The internet serves as a vast source of information for anyone looking to learn about various topics."
Alternatives: "an extensive reservoir of knowledge" or "a wealth of information".
This exercise doesn't really need to have anything to do with social media, however, I do think that the internet is a vast source of information on careers, top professionals in each industry and the top jobs/employers in your field.
The internet has a vast source of information for every kind of knowledge.
The World Wide Web is a vast source of information accessible to computers, but understandable only to humans.
This is a vast source of information about who is doing what, who is saying what, who is working with whom, and who is working with companies on the outside.
So Zeman decided to use the Internet as a vast source of product information and a means of tracking orders—and as a way to lead clients to their sales rep (whose picture appears on a customer's personalized extranet web page).
In the IHR database, prescription pharmacy claims data are linked to provide a vast source of longitudinal patient information linked to diagnosis, prescription, and hospital activity.
They limit appreciation of the subtleties and exceptions that characterise all efforts to diagnose and treat illness and displace the critical and vast source of information for treatment, diagnosis and meaningful management of illness that is found in human interaction.
While the information available in these articles (now exceeding 18 million in number) represents a vast source of knowledge, its sheer size also presents challenges to researchers in terms of discovering relevant information.
This is the new world of big data and insurance, where social media websites are vast sources of valuable information just waiting to be plundered.
And so, likely with the help of a researcher, shortly after changing his number yet again to keep ahead of his fans (note the crossed-out phone number on the notebook flap) he began thinking about this vast new source of information and images.
