Generally speaking, I believe per se that it does not - given how many authors are either doing or thinking of doing this, it may soon become the norm that agents get submissions that have already been published as ebooks. What hurts a writer's chances of finding an agent, as ever, is if their manuscript/ebook ain't that great.
If an author approached me with a book they've self-published as an ebook, I'd certainly ask them questions about why they want an agent now and what they think an agent can do for them. It's also worth bearing in mind that while agents may not have a problem with self-published ebooks, publishers may. Agents may take on these sorts of books and then discover that publishers don't want them, and that's the sort of thing you could only find out by doing. If enough publishers say they don't want these sorts of submissions, then I guess authors who want to find a publisher will stop self-publishing ... for a while.