Not long ago a close friend of mine and a very talented artist had one of her images traced. Someone ignored her comments and watermark and traced the image, linking it directly back to her dA. I browsed this person's gallery and they traced various other artist's work. All of which are on dA and many of which did not permit the use. When I brought it up politely that this was not a good thing, the artist just blocked me from their page.
This journal is sort of a PSA, I guess. I'm not against traced bases (clearly) but I don't encourage people to go on a tracing spree and trace everyone's work. Making a traced base is often times helpful (it's taught me a lot over the years) but be aware of what you're tracing before you start. If you're not aware then you may end up with a lot of fire on your hands when someone discovers what you did. Flame wars can start as artists can sometimes advertise you as a tracer (and label you a thief because of it) and allow their "following" to white knight you. This is a very unpleasant feeling.
Now, I make traced bases. I also don't mind them, but what I do mind about them is that people think everything is free game and get pissy when they're caught. There are ways to avoid a bad result though.
If you insist on making traced bases:
Can you find the artist to source the work? If you can then are they against their work being used? If so, don't use the image. Otherwise ask the artist for their permission first. Respecting others is common courtesy, yes, but it also helps your image and makes you more respectable.
Trace your own work or, if you can and have the permission to, collaborate with a friend. This helps you avoid trouble with other artists.
If you want to trace something, trace an official media image or a screenshot. You won't have to deal with anyone finding you out.
Remember that linking back and giving credit for the original image isn't always enough (in fact, it rarely is). So I stress you to ask someone before tracing their work.
Also, remember that making traced bases isn't a key to "instant dA popularity". I've seen non-doll artists do this just to get views and... in doing that you're kind of sending a (bad) mixed signal.
If you are caught using work you weren't authorized to use: Remain calm and stay polite. Be compliant as possible and don't feed into any negative conversations. Don't go bashing people even if they are nasty to you. Also remember that, when you make a base without permission, there's a high chance it'll have been used before you're caught. Keep in mind that this can make artists upset too. This is why it's very important to ask or use an official media image.
I know not everyone's good at anatomy but I do encourage trace base makers out there to try making an original base. Some of you are actually very talented and don't realize it!
TL;DR: Be aware of what you're getting into when you trace another artist's work. It may come back to bite you in the ass.