The only hard and fast rule is there is no hard and fast rule. Soon as you make a rule or define a word, someone... somewhere... will work to break it.
Is there such a thing as giving up too much control?
Depends on the relationship and the level of comfort of each individual. For those who are 'extreme' (for lack of a better word) no, there is no such thing as giving up too much. We are all shades of black, red, gray, purple, green, whatever you like. :p
Should they have your email and website subscription passwords?
Again it depends. Depends on what the sub/Dom needs. Maybe something happened to hurt the sub's trust in themselves and the way to repair it is to know that they are being looked after. I personally would have no issues turning over my passwords if requested. Depending on the site, i might even volunteer it. But, I knew my Sir loooong before he was my Sir. I would have no issues giving this as I know he wouldn't use it in a negative way. Even if my trust in myself is broken, I will always have trust in him. If that trust is broken, then the relationship is broken (and thus wouldn't be handing over passwords).
There is a caveat though. I AM responsible for anything posted under my name. If you have read Christina Parker's workbook, Where I Am Led, the very first thought of the week is "Many people make the mistake of assuming that giving up control also means giving up responsibility. No matter what the situation, a slave share equal responsibility for any consequences, either good or bad, that occur as a result of the consensual activities."
Should safe words not be used eventually?
I can't imagine, even if a relationship was 'safeword free', that there still wouldn't be a safeword per se. Even without a specified word, the sub would be able to relay the information that things are not kosher and the Dom would act upon that information as they see fit. To me, this is not much different then having a contracted safeword.
Should hard limits be pushed or ignored eventually?
Pushed? Yes. Ignored? No. If it's a hard limit that is pushed, then some discussion/aftercare/etc is needed to ensure the health of whose limits were pushed. Even for the most evil of Doms, this is required if they wish to be able to continue to 'play'.
Should your Dom/me get to choose your sexual orientation?
Your sexual orientation is your sexual orientation. No one can change it. That being said, a few things might happen. You might not be fully aware of your orientation due to a mental 'hangup'. You play with a gender that isn't part of your orientation under His/Her orders and enjoy it, whether you enjoy it or not ;) (unless we are limit breaking, if so, see above)
Once the collar is on do you give up everything or are there still things that should be left private to the slave?
Depends on how the relationship is negotiated. There are as many levels of control as there are people in this type of relationship. "We are all beautiful snowflakes" ::sees butterflies and fluffy bunnies running through the house due to all the sugar from that last line::
:rose: