Even in the rarified atmosphere that is Silicon Valley, the Instagram acquisition was unusual. Very much so. Acquired by Facebook just prior to their IPO. Lots of motivations for that, but by no means is Instagram an exemplar of anything. It's probably an outlier among outliers.
Not sure if you meant Instagram was not about to IPO, but rexreed meant Facebook was about to IPO (acquisition: April 14th, 2012, IPO: May 18th, 2012).