Bill and I were actually talking about what kind of investments GV was looking to make. He stressed that GV was looking to invest in businesses that were actually good businesses. As a counterexample, he brought up Twitter, which at the time he considered to be a "good investment" (said with a grin and a wink) but not a "good business". I had one of those feelings that you get when somebody really smart just shared with you The Truth.
Later I found myself in a conversation with Joi, I think as part of a group and not one-on-one, and Joi was talking about Twitter's lack of revenue. Joi was an early stage investor in Twitter, and he was telling us something to the effect of, "once we have all these users, we're going to bring everyone to the table and figure out how to monetize and what we can charge for."
Over the years I've thought a lot about Bill's distinction between a "good investment" and a "good business", and about Joi's "users first, money later" optimism. I always felt like Bill would be proven right in the long-term, and I think at this point he sorta has been.
Ultimately, though, either approach to investing can work -- but if you're gonna do the Joi thing, you gotta know when to get out of the trade. (I have no idea if/when Joi got out... just stating a general principle.)