Scraping/content theft is one of the arguments for absolute urls, although personally I think that any good web scraping software would be removing absolute urls by now. So the threat nowadays, where absolute urls offer an advantage, is probably more from the not so careful manual user copy and pasters. In some cases the chance of a back link might be good, in other cases you have to ask yourself do you really want a backlink from a site that just copies other sites? Is there a chance of being associated with a bad neighbourhood? You also have to ask yourself what is the inbound link value of a duplicate content page? Will the action of pasting into a CMS/blog/forum remove the HTML links (or nofollow them) anyway? It also depends on what you do when you notice people copying your content, do you embrace it, or do you try to
stop copyright infringement?
If you are submitting articles or providing RSS feeds to content, then again, absolute urls might be more appropriate.
With this whole debate I should add that in the grand scale of all things SEO, I personally do not think the absolute vs relative debate is that important for SEO, it is definitely not a major ranking factor.
One thing I should say is that there are different types of relative urls, page relative (relative to the current page), and site relative (relative to the base directory of the site). I usually go for the site relative urls, starting with a / and using the BASE HREF HTML tag to define the base url. Page relative urls (starting with a name or ..) have their uses too, but they can cause confusion if you move pages around, and can sometimes cause spiders to get stuck in loops (indexing contact then contact/contact then contact/contact/contact etc).
Here is something I
sometimes do when there is a debatable SEO issue. Have a look at the top 10 sites for the search term
SEO, to see what they do. Do they use relative or absolute urls for internal links:
1. en.wikipedia.org... relative
2. justsearching.co.uk absolute
3. seo-london.com relative
4. ihaveawebsite-nowwhat.co.uk absolute
5. google.com... absolute and relative
6. seo.com absolute and relative
7. freshegg.com relative
8. seochat.com absolute and relative
9. seoco.co.uk absolute
10. searchengineoptimising.com absolute and relative
So there is a mix of opinions in that top 10. Some of those sites with a mix of both actually have absolute urls for navigation area links, and relative urls for the main content (which kind of ignores any content scraping benefits).
Out of the many arguments for and against relative and absolute urls, the biggest myth I've heard so far, from
Bing's webmaster team nonetheless, is that relative urls do not pass on link juice. This myth is nonsense and easily disproved, at least for Google link juice, by checking things like the page rank of a section link of a high PR site, a page that is only linked to internally via relative urls and not linked to externally. (BTW there are also sites in Bing's top 10 results list for SEO which use relative urls).