Post Sarbanes-Oxley, it never makes sense to IPO, ever.
Let's go with, maybe, "Pre-SOX, you could reasonably IPO on revenue in the tens of millions with a valuation in the hundred of millions. SOX decisively removes that option. We now have economically viable alternatives to IPO, for high-growth tech companies, at valuations into minimally 'the tens of billions of dollars.' It may make sense to IPO if one is not a high-growth tech company or one desires a valuation higher than 'tens of billions of dollars.'" (Context: Uber is $25 ~ $50 billion, Microsoft is ~$375 billion.)
The a16z deck posted a couple of days ago made a great point relating to this. In the past, an IPO would allow everyone to participate in the upside (e.g., 1000%+ growth of the Microsofts and Oracles). Now, the ones reaping the rewards are the private equity groups. By the time they unload companies on the public markets, most of the upside is gone.
Let's go with, maybe, "Pre-SOX, you could reasonably IPO on revenue in the tens of millions with a valuation in the hundred of millions. SOX decisively removes that option. We now have economically viable alternatives to IPO, for high-growth tech companies, at valuations into minimally 'the tens of billions of dollars.' It may make sense to IPO if one is not a high-growth tech company or one desires a valuation higher than 'tens of billions of dollars.'" (Context: Uber is $25 ~ $50 billion, Microsoft is ~$375 billion.)