By comparing topologically trivial materials (Au, Bi, graphene) and topological insulators (Bi_1-xSb_x, Bi₂Se₃), we discuss what the features unique to topological surface states are. The properties reported so far for topological insulators are all explained by Rashba effect due to strong spin-orbit interaction and break down of space-inversion symmetry at surfaces. Topological arguments are not needed. Spin-split surface states with spin-texture Fermi surfaces, however, are very attractive play grounds for exploring spin-flow physics.