You can't impress your visitors with all the books you have. I miss that 'Wow, have you read all those books?'
Now, seriously, the only thing I took notice of when I went into someone else's house was their books. I found out about Harry Potter and Terry Pratchett that way. If everybody gets an ereader and gets rid of most of their paper books, how am going to find about books that fall out of my main area of interest? Somehow, fiddling with another person's ereader feels more like a breach of their privacy, I don't know why.