Looking at my library as it currently stands, I have 103 artists although 'Various Artists' is counted as a 104th due to my taking songs from soundtracks by 'Various Artists'. I have 900 loved tracks although some of those are wrongly named/punctuated versions of tracks from when I started scrobbling from Media Player and it took a while to co-ordinate song titles with their playable versions here on the website. If I took those out, it would lose me a heck of a lot of scrobbles so, untidy as it may make things, I'm going to keep them.
I also have some tracks that are not playable on the website such as Cancion del Mariachi by Antonio Banderas from the Desperado soundtrack, Rafael Nadal Dancefloor Superstar by Appart and the Spanish Eyes/Lola, Lola medley from the Ricky Martin live DVD "One Night Only". And of course there are tracks that were previously playable and have now gone missing like Torero by Chayanne although some of those tracks such as the El Sueño de Morfeo songs are actually playable despite being listed as unavailable.
I have discovered all sorts of new artists on last.fm - only yesterday I was recommended a new rock band ironia colombia by one of my friends who is in the band. I took a listen and the 5 songs are very promising so I added them to my library. I certainly wouldn't have found them just by listening to a normal radio station! Using this website really helps me broaden my musical horizons and as a result, I hardly ever listen to the radio nowadays, preferring instead to spend time on here where I know I can find music that will be interesting for me through recommendations and artist/tag radios. When I do find something interesting, I let my family and friends know about it too - both my mum and nephew now have last.fm accounts and we regularly swap recommendations with each other.
I look forward to finding out what my 100,000th song scrobbled will be!