Post dot come melt down the rules and requirements around financial reporting were substantially strengthened. Some of that was a good thing but in general it was an over reach. C level people now signed their names and risked prosecution. The way revenue was recognized became so conservative as to be nonsensical in many cases. The costs layered on to manage this became significant. In short, it became more and more difficult to innovate if you were a public company due to the costs and potential backlash from public markets.

Facebook is a victim of this on one end. They delayed their IPO as long as they could as Zuckerberg loathed what having to please outside investors would do to the nimbleness he requires. They then waited too long and so are now trying to excite the markets with a company that's already past its most exciting part of the growth curb. Add to that obvious greed and ego in terms of pricing as high as possible and you have a huge web blanket thrown on the ability for other tech companies to IPO.

Dell is on the other end. They decided it was better to invest 6 months of their lives into going private so that they too could innovate for the longer term.

At the end of the day we've gone from the go-go days of the 90's where nearly any tech company would IPO to a point where very few IPO either because they can't or don't want to. That will fundamentally change how companies are funded going forward and will likely impact the amount of returns being generated at the critical (for VC's) end of the funnel. My hope is that public markets realize this and begin to roll back some of the more arduous regulations.