The Daily Dot says that online manga publisher JManga sent out an email to all their users last week that included this line:

It is our regret to inform you that will be concluding its retail and viewing services. All existing accounts and private information will be deleted without further notification.

What does this mean?

The announcement informed users that all user accounts had been deleted early yesterday morning, and that all of the website's content, including popular in-progress manga series which are currently only available through JManga, would be taken down on May 30.

No, you could not get refunds for your purchased works. No, you could not download copies.

The comics that users paid for will just be gone, forever. This is the problem with e-book buying situations like Comixology and Kindle books. When you're just buying access to an e-book and not the file itself, you're not really buying anything. You're just licensing the book, and your access to it can be removed at any time. That's what's happening to JManga buyers, and if you buy ebooks from an online seller, it could happen to you, too.