OMG, this is an interesting thread.
Personally, most of you all have what I would consider to be slack parenting styles. That's cool we're all different. No one style is right. Your way just wouldn't be my way and that's good.
Would I spy on my child, no - and although many suspect the OP did this. I do not.
I have since day dot said don't lie to me. It's best to be in trouble with me than to lie to me. I can't kill you for any wrong doing, I might be able to help. I can't defend my child if I know they lie.
A 17 year old is not an adult. I lived at home till 25 I still let my parents know if someone was coming over. That is courtesy, I wasn't afraid of them they just ought to know who is in their house. How few of you get that is totally strange to me. My parents raised me they didn't raise everyone else's feral children so a heads up for them is nice.
Additionally, I have younger siblings so bringing boys home was not done willy nilly. And yes that is what hotels are for. My parents rule was not sharing rooms with boys/men So I never did (whilst they were home, but they always knew who was in their home even whilst away), does that mean they get to know whether I was and how I was having sex, no it means I let them know who was in the/coming to the house.
Courtesy on both sides should be a given.
My DS is 16, I expect any girl/boy who is going to come over to walk into my house say hello and for them to go and enjoy themselves. She will not be staying over and I expect him to have discretion when/if they have sex as there is a younger sibling in the home. Other than that let me know if someone is coming, as i'm happy to cook for more, order extra, it's just courtesy.
The house is definitely mine (and DH's), but the home is ours.