It’s notoriously hard to measure the return on investment in social media.

But a study from American Century Investments does show that financial services professionals are increasingly embracing it.

“I think everyone’s starting to accept that this is here, and it’s going to be a part of how we communicate in the future,” said Jennifer Sussman, director of online marketing and experience for Kansas City, Mo.-based American Century.

American Century’s second annual Financial Professionals Social Media Adoption Study found that 86% of financial services professionals use social media, up from 73% a year ago.

Half of those professionals, including financial planners, brokers and registered investment advisers, said they have moderate or extensive experience with social media. About 43% said they regularly participate regularly in at least one medium, with nearly 10% saying they belong in the “social media addict” category.

As was the case last year, Facebook had the highest percentage of respondents with accounts: 71%, which is up from 55% in 2010. LinkedIn held the second spot with 55%, up from 45% in 2010.

Which businesses uses of social media are on the rise? Eighteen percent of respondents said they plan to maintain a professional blog in 2011, up from 8% in 2010. Using social media for customer feedback jumped to 21% from 12%, and sharing best practices went to 18% from 12%.

Overall, the top business uses for social media include monitoring industry and market news, researching prospects, contacts and current clients, and reading expert commentary and insights.

Attitudes about the overall value of social media as a tool for business growth are also on the rise, the study shows. About 45% of respondents were generally positive about that subject. Fewer than a fifth of them expressed a negative opinion.

At the same time, few study participants ranked social media as having “high business value.” Yet the percentage that did was up two points this year, to 13%. And 56% of financial pros said they feel social media is an “emerging trend with significant future potential.” That’s up from 44% last year.

“Opinions are continuing to move in a positive direction,” said Sussman. “Social media is being seen as a trend with future potential.”

Yet financial professionals have concerns about using social media—but those concerns are changing. In the 2011 survey, regulatory or compliance issues continued to top the list of concerns, but such concerns dropped to only 38%, down from 47% last year.

Meanwhile, the percentage of financial professionals concerned about a potential privacy breach increased to 26% from 21%. Also on the regulatory front, 53% of study participants indicted that their firms have put social media policy or guidelines in place.

The study’s respondents also weighed in on asset managers’ use of social media to engage them. Forty-eight percent expressed a positive reaction, using comments such as “good idea,” “interesting” and “important.” Fifty-seven percent opined that asset managers are smart to explore social media—up from 41% last year.

And 24% said they feel that leading asset management firms are using social media to their advantage, a big jump from 11% last year.