On July 19, 2005, some members of Northwestern University's national champion women's lacrosse team were criticized for wearing "flip-flops" to the White House to meet with President George W. Bush. The women pointed out that their shoes were not "beach shoes," but were dressier thong sandals.
The use of flip-flops has also been encouraged in some branches of European and North American military as sanitary footwear in communal showers, where wearing flip-flops slows the spread of fungal infections. Following on from this, some soldiers and other trampers or hikers have begun carrying flip-flops, or a pair of flip-flop soles sewn to socks, as a lightweight emergency replacement for damaged boots
The Indian manifestation of the flip-flop, the chappal, has even been known to be deployed as a weapon, both as a truncheon and a missile, although it is more commonly merely a threat. It is not unheard of for people to whip off their chappals in the heat of an argument, in order to make their aggravation more palpable to the other party. (Touching the shoes or feet of another, in some Indian cultures, is a sign of respect or submission).
stolen from wikipedia.