I've noticed it's more international students who write their own recommendations. I've seen a few people in applyingtograd say their professors asked them to write their own recs, but I'd just feel weird about it. I mean, it kind of goes against the idea of you being reviewed by professors/people you've worked with and turns into another personal statement. If I could write my own recommendation, it would sound like I came from grad applicant heaven! Hahah.
"This student is the best student I have ever had. She embodies every trait an academic and future professional should have, and you'd be stupid not to let her in your program. STUPID. Sincerely yours, Professor X."