Stop arguing with everyone, long-term marketable securities doesn't mean what you think it means.
You're right in that it's not cash, and in some cases it's illiquid. However, you seem to think the 'long-term' in 'long-term marketable securities' means 'will take a long time to sell for fair value'. This is wrong; long-term just refers to the maturity of the instruments. Again, these long-term instruments are more likely to be illiquid, but they're not illiquid by definition. 10-year Treasury notes are 'long-term' but highly liquid.
So, in conclusion, it depends on what these "long-term marketable securities" are, which is what most of the other replies are trying to say. If you want to argue, argue that Apple owns a bunch of RIMM stock or something, don't accuse others of misunderstanding the term.
You're right in that it's not cash, and in some cases it's illiquid. However, you seem to think the 'long-term' in 'long-term marketable securities' means 'will take a long time to sell for fair value'. This is wrong; long-term just refers to the maturity of the instruments. Again, these long-term instruments are more likely to be illiquid, but they're not illiquid by definition. 10-year Treasury notes are 'long-term' but highly liquid.
So, in conclusion, it depends on what these "long-term marketable securities" are, which is what most of the other replies are trying to say. If you want to argue, argue that Apple owns a bunch of RIMM stock or something, don't accuse others of misunderstanding the term.