Normally I would say, "No, that's really shady." In this case, it seems like the initial raise was almost a marketing ploy. "Look at us! We raised $50M from these big time VC firms! We must be awesome!"
In my mind, it's not especially different from an IPO where banks put their names on the line to build the book and then get a percentage of the offering for effectively being the marketer.
Not really, no. "Follow-on rounds" are a thing. Usually with rounds more like 2x the valuation than 8x, but still. The last company I was at went out and raised 3x as much at 2x the valuation Series B while the ink was drying on the Series A. There was demand, so why not?
Hell, if nothing else the company is cash rich after the first round and less desperate for funding. You need a better offer just to convince them to dilute themselves further when they don't really need to.
Honest question?