Search Results: noticing the little things

This question is inspired by a conversation I had today with another G@G user on the topic of sharing and not sharing things with one's friends and partners.

In the process, I realized I tend to not share much with my friends, in general.
There certainly are things and topics I'm more open to discussing with someone I'm not romantically invested in (particularly the unflattering and compromising ones) but, ultimately, I'm not a great sharer overall.
Indeed this has even proven to be a crux of many of my interpersonal connections.

But at the same time, I'm much more motivated to share information with someone I may be romantically interested in, and this is true even if the motivation there is not to impress or deepen my connection with that person.
Which, upon realization, I now find odd, because I'm even less of a romantically inclined person than I'm an engaging friend.

I've noticed people's tendencies in this vary greatly, some seemingly thrive on the deep connections with their "besties" while others may sway the directly opposite way- preferring their partners being the ones who know them the most intimately.

I've dated a woman who claimed that she let me know more about herself than she did all her friends combined (in a fairly short period of time no less), admitting she wasn't a great sharer herself.
If I didn't know better from our interactions, I would have chalked this off as perhaps a little cheesy attempt at impressing me or making me feel special.

But how uncommon is this?
What is your MO when it comes to sharing things with your friends and significant others?
Does this vary from person to person and the established connection between you two?
By the nature of information, perhaps?
Do you ever make it a point to share/not share certain information with some but not the others?