This might come off as a little rude, but it's sincere advice from someone who used to work in anti-spam (not at Facebook):
I had a quick look through Dreamwidth's "latest" page (https://www.dreamwidth.org/latest) earlier today, and a major portion of the posts on there were blatant spam for things like credit card scams, "Work from home and make $1000/day!", and so on.
You seem to be hosting a lot of spam, and those spam posts are also far more likely to be getting linked externally on sites like Facebook, since that's the reason they're being created.
Because Dreamwidth is effectively free website hosting along with a free new subdomain for each account, blocking individual subdomains is futile, and it's difficult for external sites to distinguish between spam and legitimate blogs.
I'm sure Facebook will unblock you fairly soon, but unless you get the spam on Dreamwidth under control, this will probably happen fairly often with different sites blocking it. It would be easy to end up with an impression of Dreamwidth being a spam-hosting site, and decide to block it (either manually or automatically).
Blogspot has always been in a similar situation and would get blocked from a lot of sites due to the sheer amount of spam it hosts.
A somewhat related story about why text posts on reddit are called "self posts" (copy-pasted from a thread from 5 years ago where someone asked why, linked near the top of the explanation):
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It's actually a bit of a long story, but it's kind of an interesting part of reddit's history. Some of my details are probably off, but this is how I understand it.
A long, long time ago, reddit only supported submitting links. Link submissions were pretty much exactly the same as they still are now, including having a comments page that you could go to with an address like the page we're currently on: http://www.reddit.com/r/help/comments/2bmy3l/what_does_the_s...
If you look at that address, one thing to notice is that it includes the submission's ID in base-36, which for this post is "2bmy3l". If you go to http://www.reddit.com/r/all/new and look at the links to the comments pages of the newest posts, you'll notice that their IDs are increasing. For example, at the time I'm writing this, the newest IDs are 2bo3uw, 2bo3ux, 2bo3uy.
Since the IDs are increasing, you can predict which ones are coming up. You know that the next ID after those ones should be 2bo3uz. So some person decided it would be funny if they pre-constructed a link like this: http://www.reddit.com/r/reddit.com/comments/<id>/this_post_w... and then checked which IDs were coming up, filled in the "<id>" spot with one that should be used soon, and submitted it.
If they got their timing right, they'd end up with a link post that actually went nowhere. Clicking it would just take you to its own comments page, since they had managed to predict the url that the comments page would have. This was a "self post", a post that linked to itself.
So this was a pretty neat trick, and when it was successfully pulled off for the first time, it got a whole bunch of attention. Unfortunately, reddit's never been very good at just seeing some new popular thing as a novelty and moving on. No, of course pretty much everybody wanted to get their own "self post". The majority of the new submissions to the site were suddenly just people trying to make a self post, completely drowning out all the real submissions.
It was causing a gigantic mess, so one of the admins at the time decided to get people to stop by taking all the fun out of the game. They made it so that you could just choose to make a self post. You didn't have to guess the ID or anything, you just selected that you wanted to make a self post and automatically got one. It didn't have the option to add additional text or anything yet (that came later), it was just a title that linked to its own comments page.
So that's how self posts came about, and where the name originated. A quick solution to a mess being made by users that eventually turned into one of the most important pieces of reddit.
I had a quick look through Dreamwidth's "latest" page (https://www.dreamwidth.org/latest) earlier today, and a major portion of the posts on there were blatant spam for things like credit card scams, "Work from home and make $1000/day!", and so on.
You seem to be hosting a lot of spam, and those spam posts are also far more likely to be getting linked externally on sites like Facebook, since that's the reason they're being created.
Because Dreamwidth is effectively free website hosting along with a free new subdomain for each account, blocking individual subdomains is futile, and it's difficult for external sites to distinguish between spam and legitimate blogs.
I'm sure Facebook will unblock you fairly soon, but unless you get the spam on Dreamwidth under control, this will probably happen fairly often with different sites blocking it. It would be easy to end up with an impression of Dreamwidth being a spam-hosting site, and decide to block it (either manually or automatically).
Blogspot has always been in a similar situation and would get blocked from a lot of sites due to the sheer amount of spam it hosts.