At least two of Twitter's co-founders have regrets about the $2.5 billion media platform they unleashed.

Last weekend, The New York Times profiled Twitter co-founder Ev Williams, who stepped down as CEO in 2010 though he still remains the company's largest individual shareholder. In the piece, Williams laments that the site, which has more than 300 million active users, may have led to Donald Trump's controversial presidential victory.

"It's a very bad thing, Twitter's role in that," Williams admitted. "If it's true he wouldn't be president if it weren't for Twitter, then yeah, I'm sorry."

Similarly, in an interview with Inc. last November, fellow Twitter co-founder Biz Stone admitted his own regrets. In 2008, he says, Twitter started allowing strangers to tag people in their posts. Of course, this helped many users to grow their following by making connections with people they didn't already know. But the dark side of that was the creation of a fertile environment for bullying.

"We made a mistake when we added the Mentions tab," Stone told Inc. "All of a sudden, you could see anyone who was mentioning you on the site. We put the onus on users to block someone."

Stone, who left Twitter in 2011, says the company could have largely avoided becoming a so-called "Honeypot for Assholes" if they would have modified that feature earlier on.

"As soon as people started being really nasty, we should have tweaked the tab so you could see if you were being mentioned--but not by everyone," he told Inc. "Only by the people you follow, and maybe one degree out to who they follow. Because once you get to three degrees out, it's either at best irrelevant or [at worst] mean."

Twitter has come under fire in recent years for its inability to spare users--notably women and people of color--from hate speech, harassment, and other forms of abuse. This has contributed to the San Francisco-based company's financial struggles. According to Twitter's annual 10-K filing, even though the social-media company gained 2 million users during the election cycle, it lost $467 million in 2016. Although co-founder and CEO Jack Dorsey recently unveiled new tools aimed at combating abuse, it's unclear to what extent these have had an impact.

Just last week, Stone--who recently sold his company, Ask Jelly, to Pinterest--announced he will be returning to Twitter, in part to manage the platform's reputation. (He declined to comment further on his new role when contacted by Inc.)

He will have to grapple with how to tame his and his co-founders' creation. At a commencement speech given to the University of Nebraska in May, Williams compared Silicon Valley to Prometheus, the deity of Greek mythology who stole fire from the gods and passed it on to mortals. "What we tend to forget is that Zeus was so pissed at Prometheus that he chained him to a rock so eagles could peck out his guts for eternity," he told the students. "Some would say that's what we deserve for giving the power of tweets to Donald Trump."