To pretend like he is "forced" to diversify is to completely ignore the scale of those companies. Just adding those 5 up is an order of magnitude off from his net worth.
I'm not taking a side or making any point other than that particular logic doesn't work here.
Yeah... no.
Imagine you have a lot of money and considering buying 4000 ASICMINER shares. That's just 1%, but it's still not easy. In fact, it's going to be very, very difficult. Even if you to buy at 2.2 per share (slightly above the price at btct) you might not even get 500 in one day.
If you try to spread it out in a week or so you might end up paying say 2.5 per share. If you spread it out in a month you won't really get a good deal either, because ASICMINER would probably still rise at an uncomfortable pace.
Even if you still decide to spread it out over a relatively long time frame, you'd be sitting on an idle pile of money for some time; if there's something better while you're waiting, you'd like to put your money there.
To actually get a good deal you probably need to talk to some large shareholders who is thinking of cashing out, and be careful not to advertise so much that the share price rockets up because you're too famous for being rich, or really be patient with your buying strategy. Both of these happen quite a lot.
Now Warren Buffett probably faces this quite often. Every time a new pile of cash arrives at his hand, he has to think of ways to turn them into shares. Then there's the painful time of cashing them out; if you try to sell 4000 shares of ASICMINER-PT on btct at once, you see most of your shares turning to peanuts.
"Comparable to the market value" was more of a matter of speech, because even with one tenth of his wealth it's not an easy task to turn all money into shares of a handful of companies at good prices.
