Is href required on links?
Yes. Anchors without href attributes are not links.
I'm asking this because I have some links that act like buttons that pull out content trough ajax
If you are doing that, then do it right. Use Unobtrusive JavaScript and pushState.
"Links" that only work if you are using a pointing device and have JS turned on are not good links.
I'm asking this from the SEO perspective
Search engines won't execute your JavaScript, so the pseudo-links (which depend on JS) are just black holes of nothingness as far as they are concerned).
