回复：大家有没有向不认识的人要过推荐信，

I tried one time. But I didn't asked plainly from the referee to write a letter of recommendation for me. Instead, I wrote to apply a postdoctor position from him, and asked him to evaluate my qualifications no matter he would offer me or not. The professor didn't have funding at that time, but he still felt happy to provide his evaluations in his responding letter. It's only a couple of sentences. I used this as a supportive document for my 140 petition. It worked out. I think this kind of document is even more important than the letters from your acquaintances because in these days, INS attached increasing importance to the idependent judgements.