My suggestion to help minimize this issue would be as follows :

1. Disallow links in WYSIWYG unless they are properly referenced using the UI.
2. When adding a link with the UI, force additional information to be added with it (Title, Long description + Code, etc)
3. On save, SO should check the link against Short URL services, and then against a malicious site filter (similar to AdBlock), and if something found, flag the user for spam, and hide their answer for moderation.
4. Before database insert, check if link is alive, and download a page preview (like Facebook, and other services do), and attach that with the URL.
5. Lastly, for inactive threads, on first browse after so much time has elapsed, run the links through those checks again (#3, and #4)

I have implemented this mechanism on several clients WordPress sites and it works like a charm. No more spam, but open threads. Link posts show the user what the link is going to, and posts are automatically kept hidden and flagged for admin if a someone goes through those steps with a spam/viral/malicious link.

Having this implemented is really not that complex (code-wise), however I think there are a lot of politics involved for something like that to be implemented on SO. (like, this post would probably require at least a million upvotes)

The answer to your question is Yes and No.

The examples you supplied, are clearly not an appropriate or complete answer (noting the one that got up-voted as well).

Generally, links are for reference, and Answers are for Solutions. If an Answer only contains a reference, then I would not consider that as a Solution except in certain cases (example Q/A below, which would be valid in my opinion)

Some cases do not require a lot of explanation, and a link would suffice provided that link is RELIABLE. However your points about spam and malicious links are valid. Additionally, links expire, sites go down, pages get moved, and so forth which all affect the quality of the response.

A good example of a valid link with a short response to a question may be something like :

Q: Where do I go to sign up for an S3 API account on Amazon ?

A: To sign up for an S3 API account on Amazon, go [link here]

To help minimize this issue from the posting side, try and phrase your questions so they don't encourage responses with links only, or state in the question that you wish for the complete solution to be self-contained in the Answer post, and that answers that are not in this form will not be accepted.

My suggestion to help minimize this issue would be as follows (from SO admin side) :

1. Disallow links in WYSIWYG unless they are properly referenced using the UI.
2. When adding a link with the UI, force additional information to be added with it (Title, Long description + Code, etc)
3. On save, SO should check the link against Short URL services, and then against a malicious site filter (similar to AdBlock), and if something found, flag the user for spam, and hide their answer for moderation.
4. Before database insert, check if link is alive, and download a page preview (like Facebook, and other services do), and attach that with the URL.
5. Lastly, for inactive threads, on first browse after so much time has elapsed, run the links through those checks again (#3, and #4)

I have implemented this mechanism on several clients WordPress sites and it works like a charm. No more spam, but open threads. Link posts show the user what the link is going to, and posts are automatically kept hidden and flagged for admin if a someone goes through those steps with a spam/viral/malicious link.

Having this implemented is really not that complex (code-wise), however I think there are a lot of politics involved for something like that to be implemented on SO. (like, this post would probably require at least a million upvotes)