Spending a lot of time alone, or unable to speak normally about our favorite subjects, we can lose some self-awareness when it comes to conversation. Forgetting how nice it is to speak easy and fluent English and immersed in Peace Corps culture, we tend to ramble at length about tedious subjects only another volunteer could appreciate or find interesting, and we can forget how to notice we're boring the pants off every non-volunteer in the room (and sometimes the volunteers too). Every volunteer gets this to some degree, some worse than others.
The other issue is the "village voice." (This may only apply to English-speaking countries.) Here most people speak at least some English, but people can be easily confused by rapid-fire American speech, so volunteers learn to speak slowly, enunciate, and use simple words. This is great for the village, but it tends to infect the rest of our speech and make us sound either stupid or condescending.
I have found that, though I surely talk too much about Peace Corps like anyone, my larger problem is even more boring. If you're reading this you probably realize that I consume a vast amount of nonfiction, politics, or otherwise nerdy material. I've had this habit for years, but one way I deal with it without developing any serious problems is talking it out with friends. In college, I could have one or two conversations (no more! I could stop anytime!) about the Mexican drug war, or the latest Joseph Stiglitz book, or the latest civil liberties outrages, without endangering any friendships.
Here, though, with so much time spent alone, the trivia builds and builds, until when I spend a vacation with friends I find myself talking literally all day, almost unable to stop. It's a jarring experience for someone who was once considered notoriously reticent. Blogging, I think, is providing the small relief from this backed-up trivia that is keeping my few remaining friendships intact.