the knee down effect is not that hard when u learn thru practice to do it..its a natural effect of physics like gravity in this case its centrifugal effect ..if u take a tight turn fast enough theres no other choice of taking that turn without getting crashed other than kneeling down the bike up tou your knees or elbow for adding support & stability while in hard turn.. the danger is coming out of that turn when u get so excited that u wanna rev it so hard that u can loose control...or the other opposite side of it,, when we get caught off guard bwfore the turn & we do not take the right race line or Id say the APEX of the turn ( which is the middle point of the two extreme points of the circunference of the turn dat makes a straight line (dat straight line is da race line)or if u can imagine id say the middle point of point A & point B ; a straight line between both points of the semi circunference of the turn..dats the race line in ... the stiffer the turn the shorter our trayectory in dat turn..& dats why we need to lay down the bike with the elbow to stabilize the centrifugal effect otherwise we would just miss the turn & straight to the grass... I'm not a pro racer but dats what i learnt when i took racing class... ..
if u didnt understand what i said just remember look at the point in da road where u gonna start da turn & then just look at the end of dat turn... dats it... point A then look at point B .. u will cut dat turn in just a stright line (but ur bike will be layed down during dat turn...the harder the turn the lower the bike) & at the middle of dat turn ur bike should be at the APEX point or id say the center point of dat line... also your head possition during the turn is a critical part of it... ur head should be 45 degrees turned & ur eyes just focusing the Point B or da point where dat turn ends..
hope this helps try doing it safely at the racetrack... dats the best way to maximaze speed during turns... the dragging part of elbows & knees .. it just make u look gud in pictures..hehe