I'm also 26, and I definitely relate to the teenage IM experience. I think the problem with phone calls is that it's an unnatural level of focus to give someone you don't know well. when you meet face-to-face, there's always some little distractions available to fill the gaps in the conversation. silence is way worse without context; after fifteen seconds or so, the other person will say "hey, are you still there?" I also find myself missing one word out of every other sentence the person says, so there's a lot of backtracking.

as an aside, I've noticed that my cohort of people who grew up sending hundreds of messages/texts to their friends every night don't really interact that way anymore over text. back then if the person was online, they would usually respond immediately and you could exchange a lot of information really fast. now every response seems to take a few minutes or an hour (I do this myself too, don't mean to blame anyone). it has the weird effect of making text a less useful way to communicate than it was ten or fifteen years ago. I guess when everything is immediate and urgent, nothing is?