I have a library thats just a little bit smaller than 18k tracks. I just signed up for iTunes Match and am currently waiting for step 1 of 3 to complete. In the mean time I went onto my MacBook which doesn't have any of my music library on it, and signed into iTunes Match. Much to my surprise it says I already have 147 songs in the cloud. Upon closer inspection only two of the songs are songs that I actually own and both were purchased from iTunes. I'm not quite sure where the other 145 songs came from though? Seems very weird to me! Edit: Upon even closer inspection I realized that these are songs I got for free in 2006 from the Facebook samplers or whatever. I didn't end up liking any of the music so I deleted it all and forgot all about it until now.