"I have my fingers crossed that they, Instagram, will listen to the voice of the community and reverse the new terms of service, but I'm not holding my breath," wrote photojournalist Richard Koci Hernandez, who has more than 163,000 Instagram followers. He shared his thoughts Tuesday on Instagram, where he was posting blank black squares instead of his usual artful black-and-white images.

"I don't feel like debating the terms of service or being too nostalgic about the old days of Instagram, I feel that it's much better just to take our work and more importantly friendship and conversation to another place that respects our rights and ownership as creators," Hernandez added. "Let's move the party to a new location."

Bloggers also were spotlighting tools like Hipstamatic and Camera Awesome, as well as Twitter's own new photo service that includes Instagram-like filters.

A year-and-a-half-old blog post from photo-sharing site Flickr was also making the rounds. In it, Yahoo, which owns Flickr, uses language, perhaps aimed at Facebook, that says "(w)e feel very strongly that sharing online shouldn't mean giving up rights to your photos."

Systrom said Instagram agrees.

"Instagram users own their content and Instagram does not claim any ownership rights over your photos," he wrote. "Nothing about this has changed. We respect that there are creative artists and hobbyists alike that pour their heart into creating beautiful photos, and we respect that your photos are your photos. Period."

It is, of course, too early to know how many people were fleeing Instagram on Tuesday. But anecdotal evidence suggested a movement was afoot.

Instaport, a tool that lets users export and and download their Instagram images, was reporting overtaxed servers Tuesday morning.

"Our servers are very busy right now, so it may show you some errors," the company wrote to a user on its Twitter feed. "Please try again later or tomorrow."