Big companies put a lot of money into on-campus recruiting, and small companies with smaller budgets stake out digital space to try and reach college talent as it funnels into the workforce. So it's somewhat surprising to see that college students still rank word-of-mouth as the number one way they learn about companies.

According to Sanjeev Agrawal, CEO of career platform Collegefeed, in a post on the HBR Blog Network, more than 70 percent of students and recent grads cited friends as one of the top three ways they learn about companies. Job boards came in second, at just under 70 percent, and campus visits ranked third, with less than half of students responding with that answer.

About 15,000 students and recent grads responded to the Collegefeed survey.

Those responses might raise eyebrows in a digital age that affords companies every opportunity to get their name out there through social media and other digital opportunities, not to mention the inroads they look to make on campuses.

"These results blew us away," Agrawal writes. "Most companies (almost 100 percent of the large ones we spoke to) say that they have an on-campus recruiting plan and that is where they focus their sourcing and branding efforts. Many also have dedicated organizations to build relationships on campus."

That isn't to say they're looking to follow their friends into their companies, however.

The same group of respondents ranked "alumni and friends" at a company as the last thing students were looking for at a company, even if friendships serve as the top way they learn about companies. (The top choice in that category was cultural fit at the company. Career potential, followed by work/life balance, followed.)

That presents a little bit of a convoluted scenario. The survey shows that students learn about companies they might want to work for through friends, but that they don't really care about working at the same companies as their friends. They also want to work for companies with great cultures.

Connecting the dots, this might indicate more than anything the sort of chatter that is going on among job-seeking millennials. It might be that they're talking about the culture at their companies, and that sort of word-of-mouth is enough to turn a recent grad's eyes toward the career section on a website.

If so, that speaks volumes to the importance of growing a happy, healthy culture not just for the sake of the employees you already have in the door, but for those you might want to eventually bring through it.