"Who you know" can definitely help you in finding an internship or a permanent job. I definitely recommend building your contacts and constantly growing your network circles. LinkedIn is great for maintaining and growing your contacts. But also leverage other social media channels. Remember that anything on your social media accounts may be viewed by a prospective or current employer, so be careful what you post. During my career, I have had found most of my jobs/positions through networking. So "what you know" will help you do the job, but "who you know" will get you the exposure to the opportunity in the first place. So you do need both. "What you know" is your skills and experience -- what you would put on your resume. After you get a job, "who you know" within the company is critical to your success and ability to get things done -- for example, knowing who to include and when in order to foster collaboration, teamwork, and getting the right "buy in" and approvals when needed.