It's probable that the practice of not turning your back to the Eucharist comes from the protocol of showing a king or other royal person respect and obeisance through a similar practice. Generally, to leave the "royal presence," a person would back away a few (or several) steps before turning to leave, although some who wished to show deep respect or homage would not turn their back toward the royal person at all while in their field of vision.
If the room or area for Adoration is small, I would agree that one should avoid turning your back to the Eucharist if at all possible, out of respect and as a reminder that He is our King and the focus of the room (and, hopefully, our lives).
When leaving the church after Mass, we still genuflect toward the Tabernacle, but we usually aren't within that smaller, closer area, so it's not seen as an insult or show of disrespect to turn and leave afterward--not to mention, it would be rather impractical to walk backward the whole way, especially in very large churches! ;)
While I appreciate the reasons for the practice, and think the reverence shown for the Eucharist is a good thing, I also don't think it's absolutely necessary to do all of this in order to show respect and homage to Our Lord. Geneflecting upon entering, crossing the room, and leaving, is sufficient, IMHO.