My FS cancelled my second IUI with four follicles. Three was his limit, and to be honest I didn't really question him about why the number three. I have to admit I probably would have freaked out the whole 2ww if I had gone ahead with four!
My FS also encouraged only one transfer for my IVF transfer, but it was a fresh not frozen transfer. I would really love for my frozen transfer to do two embies, but I can practically hear my FS argument against in my head now!! Logically I know I'm still young and don't need to rush things, and I get the risks associated with carrying multiples (not to bothered about actually HAVING twins, just the complications freak me out!!)
I too have heard of patients overseas transferring CRAZY numbers of embies. It amazing how standards can vary so much in other countries!! I guess it depends so much on your personal circumstances. I guess the drive o be successful will make people agree to crazy things.