What happened to me while head of the popular online forum Reddit for the past eight months is important to consider as we confront the ways in which the Internet is evolving. Here's why:

The Internet started as a bastion for free expression. It encouraged broad engagement and a diversity of ideas. Over time, however, that openness has enabled the harassment of people for their views, experiences, appearances or demographic backgrounds. Balancing free expression with privacy and the protection of participants has always been a challenge for open-content platforms on the Internet. But that balancing act is getting harder. The trolls are winning.

Fully 40 percent of online users have experienced bullying, harassment and intimidation, according to Pew Research. Some 70 percent of users between age 18 and 24 say they've been the target of harassers. Not surprisingly, women and minorities have it worst. We were naive in our initial expectations for the Internet, an early Internet pioneer told me recently. We focused on the huge opportunity for positive interaction and information sharing. We did not understand how people could use it to harm others.