If the centrepiece of your legal defence is "we're just like a library" it would probably help to behave like a library: for example, if you purchase five books or CDs then lend five copies at a time.

The IA doesn't appear to buy many books or CDs or DVDs (it has donation drives for second-hand copies). It doesn't do any controls over the number of copies "out". It resembles MegaUpload or other piracy sites more than a library.