True, but shouldn't Twitter have more potential future earnings than Groupon?

How do you figure? Twitter seems like a pretty typical example of a tough-to-monetize service, whereas Groupon is already outrageously profitable.

groupon's business revolves entirely around selling things, with limited social aspects to make it enjoyable. Twitter is literally the exact opposite. There's no clear way to monetization for them.

Thanks for that answer. I understand this, but I just keep thinking why can't Twitter just but a few display ads like Facebook to monetize?

facebook has ridiculously useful demographic targeting information. Twitter is a little bit more messy and it would be trickier to target as accurately, so the value is less there

That makes sense now that it's been explained, thanks!