Despite needing each other, Twitter and Instagram are feuding, and Instagram has gone so far as to disable an integration tool, leaving pictures difficult to view on Twitter.
The microblogging site said Instagram disabled its Twitter Card integration tool, which affects how Instagram photos appear on Twitter. "So when users click on tweets with an Instagram link, photos appear cropped," Twitter reported.
A Twitter spokeswoman declined to comment beyond the company's status update.
Instagram CEO and co-founder Kevin Systrom said the company wants to create the best experience for its users but also wants users to spend more time on the Instagram site.
"A handful of months ago, we supported Twitter Cards because we had a minimal Web presence," Systrom wrote in an email. "We've since launched several improvements to our Web site that allow users to directly engage with Instagram content through likes, comments [and] hashtags, and now we believe the best experience is for us to link back to where the content lives.
"We will continue to evaluate how to improve the experience with Twitter and Instagram photos," he added. "As has been the case, Instagram users will continue to be able to share to Twitter as they originally did before the Twitter Cards implementation."
In June, Twitter launched Twitter Cards, which are, in part, geared to improve the look of images posted on the site from partnering websites. According to Twitter, the cards also can drive traffic to the partnering site.
Relations between Twitter and Instagram got more complicated in April when Facebook bought the popular photo-sharing app company for $1 billion.
And it might not have helped when Instagram experienced a dramatic uptick in popularity among mobile users this year and pushed past Twitter in the mobile user race.
Instagram, which is just two years old, went from 886,000 daily mobile users in March to 7.3 million in August, a nearly 8.5-fold increase, according to comScore, an online tracking and analytics company. That growth put Instagram ahead of Twitter, which had 6.86 million daily active mobile users in August, an increase of 24% over the same six-month period.
"This is a manifestation of the inherent conflict in social media, or on the Web in general," said Ezra Gottheil, an analyst with Technology Business Research. "You want to get traffic from other sites, but you want people to have a reason to stay with you. They have to work together, but they also have to give users a reason to go to their own sites. Those are often conflicting goals."
Instagram wants people to see its images on Twitter and then come to Instagram and ultimately Facebook. Twitter, however, wants people to see the images on Twitter and stay on Twitter.
Gottheil said this feud is more about competition than it is a bitter, gun-slinging Hatfield-and-McCoys style rivalry. It isn't about revenging a wrong as much as it's about marking territory, he said.
"As the Godfather said, 'It's just business,'" added Gottheil.
Sharon Gaudin covers the Internet and Web 2.0, emerging technologies, and desktop and laptop chips for Computerworld. Follow Sharon on Twitter at @sgaudin and on Google+, or subscribe to Sharon's RSS feed . Her email address is email@example.com.