Maybe I don't understand these investments but I don't think that makes any sense. Presumably the 171m that's been invested in Groupon hasn't bought the whole company, only a proportion of it, so the investors only get that same proportion of the 5bn. For example if that 171m represents only 10% of Groupon's shares then the investors only get 500m back; a 3x return rather than a 30x return.
While true, I doubt investors own only 10% of Groupon, especially not at a $171M stake. Groupon had (at least) two cash injections, one for $1M in seed money, the other for $135M. The last round was for 10%, which gave them a $1.35B valuation in April.
