My cousin was married a little more than a year after beginning to date his now wife. They met and started dating in the summer of 02 and were married in September of 03. My best friend was married almost a year to the day of starting to date her husband (married for four and a half years now). And my parents married four months after they met (married for 28 1/2 years).
A year isn't too soon, I don't think. If anything, I think some people drag it out too long. Unless you're really young (by which I mean late teens), three and four years seems excessive to me. You generally know within a few weeks if it's just not going to work, a few months to know that it will. Maybe a little longer to be really sure, but I think most people just know (not immediately, but sooner rather than later).
I know "they" say it takes 9 - 12 months to plan a wedding, but even a big fancy wedding doesn't have to take a year to plan. My cousin's wedding was planned in about 5 months, and it was super fancy schmancy and with about 300 guests.
Are you ever really ready for life together? In some ways, sure, but really, if you wait till you're absolutely ready, you'll never do it.
I actually think the average time increased during the latter half 20th century, and has only recently come around to being back to "normal." Ever hear of the phrase "one year from first date to wedding date?" Pretty common back in the day. I just think more and more young couples are saying, "we know now, so why wait?" All this, "I know we're going to get married, just not for a few years" is pretty ridiculous, IMNSHO. If you know you're going to get married, get married already! Many of the couples I know in the three and four year stage of their relationships have long been saying they know they're going to get married, and have known for a long time. Why the wait?
Honestly, if I'd been dating someone for a year (not married within a year, mind, but dating for a year), and we weren't engaged or close to it, I'd wonder what we were doing still dating.