So in practice what do many people do? First they look back nervously every few seconds causing an even GREATER distraction than if they would just step back. But people are NERVOUS and they feel like they are bound to their place and anxiously await the liberation of three steps back and עושה שלום. Then if the person doesn't finish quickly enough the person in front will just take his three steps back anyway - usually sideways, which according to the Mishna Brura is also not allowed.
So what to do? First of all relax. Enjoy the sensation of being alive! Then remember that as long as you haven't stepped back you have a דין of being לפני השם. AHHHHHHH how pleasant to stand in the presence of הקדוש ברוך הוא.
Now we move a step further [pun intended]. The Tzitz Eliezer [ חלק ט סימן ח] in his simply breathtaking scholarship found a few reasons to permit one to step in front of a davener [if necessary].
1] People today don't have so much kavana to begin with so stepping in front of them won't really distract them [it might even wake them up...].
2] If a person is davening with a tallis over his eyes [men and Conservative women rabbis] or his eyes are closed [applies to religious women too, although I've noticed that women often daven with their face buried in their siddur which I rarely or never observe men doing. (Why is that gender distinction so?) This would also allow someone to pass before them.] it is also not going to be a distraction. [Is it מותר to put parentheses inside of brackets? (I just did it):-)]
3] A person standing in front of the door or any other public thoroughfare has no right to stop people from passing through and therefore one may step in front of him.
עיין שם בציץ אליעזר וינעם לך!
Love and blessings
