Liposomes are closed vesicles formed by lipid bilayer membranes. They have been well studied as simplified models of biological membranes, and are used in various applications such as carriers of drug delivery. Recently, a variety of novel transformations has been found on liposomes in the course of their solubilization by surfactants, i.e., liposomes exposed to various surfactants exhibit continuous shrinkage accompanied by intermittent quaking, opening up of the membrane, and inside-out topological inversion. To elucidate the mechanism of these phenomena, I have analyzed a theoretical model based on the bending elasticity of the membranes. When the line tension acting on the edges of membrane holes decreases due to the effect of surfactants, stable holes are formed in the membranes. On the other hand, water leakage through transient (unstable) holes may account for the intermittent quaking of liposomes, because it causes a relaxation of the membrane tension and an increase in thermal fluctuations of the membranes.