I believe that recommendation letters should be only given to whom you have directly interacted and dealt with either at work, school, company, etc.

It's wrong to give a professional recommendation to the one who you never had any professional familiarity before. However, if you're familiar with one's articles, or had detailed discussions on the professional subjects, or co-authored books or articles, or had a number of communications while being in the same professional community, and have a firm believe that this person is honest, professional, and ethical - perhaps, that's enough for a recommendation.

Recommendations should be based on the experience you have with the seeker. Giving a recommendation letter to another colleague based on a third colleague word of mouth or even CV is undoubtedly wrong and even threatens your integrity if that person happens to under-perform in whichever institute he/she gets employed/admitted in.

Mohamad Hani - It is absolutely wrong to give a recommendation letter to another colleague based on a third colleague word of mouth and CV if you have never worked directly with the person. Recommendation letters should be given only to those persons whom you know professionally and personally and have full confidence on them and you have a consistent good relations with them. One has to be very cautious and must not come under influence or pressure of any sort while giving recommendations.

It is wrong to give a recommendation letter to another colleague based on a third colleague word of mouth and CV if you have never worked directly with the person.