I found this interesting and eye opening article written by Mary Malia for "Your Tango" where she talks about the random assumptions people have about lesbians... I've scaled it down to just the list;
1).Men molested us as children and that turned us into lesbians.
2).Lesbians hate men.
3).In every lesbian couple, one has to be the man.
4).Lesbians just haven't been with the right guy yet.
5).Every lesbian uses strap-ons and dildos to take the place of me.
5).No lesbians ever use strap-ons.
6).It's not real sex if there's no penis.
7).Every lesbian relationship has a butch and a femme, because someone has to be the man and someone has to be the woman.
8).Lesbian bed death happens to all lesbian couples.
9).Lesbians want to have a threesome with your bi-girlfriend/boyfriend because we'll have sex with any woman around.
10).Pretty women can't possibly be lesbian.
11).Lesbians don't wear lingerie.
12).Femme lesbians are pretending to be lesbian.
13).All butches have short hair and are overweight.
14).All lesbians hate make-up, shaving, bras and dresses.
15).All lesbians like camping.
16).Lesbians drive SUVs like Subaru Outbacks and Jeep Wranglers.
17).Lesbians are all into sports.
18).Lesbians all dress like men.
20).The L Word television show is a real-world depiction of lesbian life.
21).Lesbians try to "recruit" straight women.
22).Lesbians are no fun, angry, rude and insensitive.
23).Lesbians are all crazy and will stalk you and ruin your life.
24).Lesbians were all tomboys as children.
25).It's just a phase.