Fluid nature of membrane is useful in 
a) Cell growth 
b) Formation of intercellular functions 
c) Secretion 
d) Endocytosis 
e) Cell division

Fluid mosaic model was proposed by Singer and Nicolson in 1972. According to this model the quasi-fluid nature of lipid enables lateral movement of proteins within the overall bilayer. The fluid nature of the membrane is also important from the point of view of functions like cell growth, formation of intercellular junctions, secretion, endocytosis, cell division etc.