I registered to deviantART 9,5 years ago and I've just removed all of my submissions today.
deviantART was - and still is - a miraculous place. You're surrounded with art, photographs, illustrations, from amateur scratches to masterpieces, from all around the world. It's a perfect place to go and just get lost in the flow, click by click. You can find any kind of art there, from portraits to linux software themes, and it's also one of the currently active sites with the longest memory, going back 14 years.
I've joined to be able to look around and only started uploading anything years later. I had two reasons: that time I believed I might want to do photography for a living, so I wanted attention; and I wanted to see if I could sell any of my pictures. I even thought to use deviantART as my main profile site for a little while ~6 years ago.
Neither of them worked, mainly because my photographs were not good enough to hold people's attention but also because it is way overcrowded. There are brilliant photographers on that site, just left in the dust.
And it's also a silo, a walled garden. They have DMCA address and even when you're clicking a link to an artist's website you're reminded "You are now leaving deviantART.com. Be warned! Out there be monsters.". Even Facebook stopped doing this. The other thing is don't get is the internet-in-the-internet effect. How often do you come across with a pictures from deviantART in Google Image Search? Only if the subject or the artist matches. No tags, no metadata, just like Instagram1.
I still love the art on deviantART, but not the site itself; those days are passed. We'd be better off with an art aggregator, pulling individual artist sites, without potential licence issues2 but with the wandering around in art effect in place.
UPDATE (2014-07-11 12:33)
A few hours after I published my post, I received a mail from deviantART. ( I was so surprised I checked the mail server logs if it was really coming from their servers; it was. )
My name is [...], and I work at deviantART in Marketing. I came across your blog post outlining your reasons for leaving deviantART. I wanted to let you know that we've passed this information along to our Product team.
We really appreciate your insight and we're extremely sad to see you leave deviantART after 9.5 years. If you have any additional thoughts or suggestions you'd like to pass along, please feel free to share anytime. Also, if you reconsider leaving, let us know!
Thank you for your thoughts and time.
[...] ( I removed the name from the letter for privacy reasons. )
This is very rare and very surprising in a good way: deviantART is out there, listening to all of our voices. I believe none of the other social networks or photo/art sharing site would have done this.