RIS and BibTeX uploads are treated as "unchecked" - i.e., potential spam. DOIs are parsed automatically and checked if possible. This means that there are two "categories of articles in CiteULike: "checked" and "unchecked". "Checked" articles offer more features than "unchecked", so when adding to CiteULike, the way to go is:
- If this fails, use DOI (My CiteULike: Post URL).
- If this fails (because what you want to cite doesn't have a DOI) use RIS or BibTeX (but these citations will be second-class citizens in some respects).