The software involved is more of a key issue. You can always get more machines off the shelf, but you can't just go to Dell.com and place an order for a few killer algorithms. If you have awesome software, you can get funded. IIRC, Powerset is already backed by some big players.
The infrastructure behind Google, Yahoo and even Microsoft is not just a bunch of machines plugged to the same Ethernet switch... They're building datacenters from scratch.
Sure, but it's still an easy problem. Building big data centers is definitely a problem these guys face, but it's by far not the biggest or hardest one. The software infrastructure and algorithms are much more daunting problems.
Let me remind you that Google was a small startup very recently, and that was during the "dot com bust".
