I don't think his point carries very far. Look, people are running large, successful web sites using PHP. What more proof do you need that performance is irrelevant?
However, the "sweet spot" for acquisitions seems to be when your business reaches the 20-100 server range. LiveJournal, Wikipedia, Meebo, Flickr, etc. all seem to be around that size.
That's precisely the range where scalability does matter and performance doesn't. You've outgrown the put-web-and-DB-on-separate-boxes-and-replicate approach, so you actually have to think about partitioning & shared-nothing. But 30 servers @ $200/month/server is only about $6000/month, the cost of a single employee. At this stage, it doesn't really make sense to sacrifice developer hours for operational costs.
If you get to be really big, it makes a whole lot more sense. 100,000 servers @ $200/month/server = $20M/month, more than the purchase price of a small smartup. At this point, it makes a lot of sense to put a team of a half-dozen or so programmers onto the problem of speeding up individual server performance. If you can double performance, you save $10M/month, which'll pay wages for close to 1000 programmers.
There's a reason why Google writes all their performance-critical stuff in C++.
