I've noticed this with women, always younger single ones, not granny ladies nor mums - and I am a very right-on non-sexist type of person... but in this area its more a look of annoyance than a blast of the horn or anything like that.. I get the impression they see being "held up" by a male cyclist as an extension of the glass ceiling and that cycling is a "testosterone charged" thing, although I don't go around in lycra (I'd feel it was indecent and even if I were brazen enough to wear it would have to go for a Vladimir Putin style fitness régime before I'd be happy going out in the street dressed like that

)