I’ve been making an effort to scrobble the majority of my listening since 2007 and I know many of you started before then. It was a great tool for discovery - I’ve found a few of my current favorites through the service, most notably Porcupine Tree and Steven Wilson and much of the music that branches from there.
Apparently our friend Last.fm turned 20 last weekend!
Well you got in a year before me, and I love to get my Scrobbles in too.
Been a Pro subscriber for a year and really enjoy the insight on what I have been listening to.
What a great service.Just checked and my first day of scrobbling was December 31, 2009. Interesting that this is my very first scrobbled song (from my New Year’s Eve playlist):
Happy New Year, Baby by the Johny Otis Orchestra. Played at 7:36pm. Must have been about the time the party started. 
My first track was #34 by Dave Matthews Band on July 10, 2007. The playtime is recorded at 4:53 am, which I know can’t be correct. My guess is that the scrobbling was happening asynchronously or manually at that point. I think I remember having apps on my Mac that I had to interact with to send scrobbled tracks up to their servers. 189,410 tracks since then. Re-upped my Pro subscription a month or 2 ago, I had a subscription for a while once upon a time. A great service, I agree!
also a pro subscriber here … still a good service, but I can not understand why they are not showing what your friends listen to anymore. A few years back, on your home page, you had an overview of what your friends listened to recently or their favourite tracks. But that’s gone, and I really don’t get why. Instead it’s all half assed recommendations and old blog posts.
I guess CBS bought it and didn’t do anything with it.
and: scrobbling since 22 Feb 2005 … my first track, a mistagged Doujah Raze - 360%b0 
First Scrobble Saturday 20th December 2008.
Apparently ‘Audio Alchemy’.
More historical research required… 