Well, this is how I see it. Knowing how many partners they have had is okay. If they tell you and trust you with that information.. But to take it beyond just knowing I.e: making them tell you about them, asking how many times, making them feel guilty about it. That is never okay. Knowing is okay. Because we are curious by nature, and it is your partner, you will learn everything about them. But you can never force it. Ever.