The reverse of this is "severely deficient autobiographical memory", which has been in the news recently as well (and I think discussed on HN too).
I think it's interesting that I consider myself to have a good memory but it is by far best at verbal associations (e.g. facts about a specific topic, object, word, or concept). The autobiographical part feels quite weak for me: I often find it hard to remember experiences in my life "by theme" (e.g. "think of a time when you felt X", "think of a time when you did Y very well or poorly"), and I very often don't remember what year a particular thing happened, or who was present with me on a particular occasion, or what I have or haven't done before with a particular friend or family member. I certainly have many vivid memories from my life, but they don't seem to be indexed that well by date, topic, or person.
I've been lucky enough to travel frequently, but I feel like I would be unable to answer questions like "how many times have you been to country X?" or "in what year did you first/last visit country Y?". (But I would probably be able to draw a decent map of specific places I've been, on various scales, and remember specific restaurants, train stations, landmarks, foreign language vocabulary, impressions of history and culture of various countries, etc. -- just not necessarily things like "when did you go there?". For example, my nephew recently asked me my impressions of Singapore, and I wrote him a six-page letter in reply with tons of particulars about all sorts of aspects of life/culture/politics/geography of Singapore, but I was unable to remember what years my trips there took place.)
Anyway, all this reminds me that "having a good memory" is definitely not just one thing!