Netcraft thinks that infrastructure is a driver in the Six Apart-LiveJournal Deal:
So how does Six Apart benefit? LiveJournal has 93,000 paid accounts, which are priced at $25 a year - around $2 a month, or about $190K in monthly revenue. That number is more impressive when infrastructure costs are included. LJ's revenue stream is focused in 3.8 percent of its active accounts (which number 2.44 million, rather than the oft-quoted 5.6 million figure, which includes inactive accounts). Those paid accounts essentially subsidize the other 96 percent of users - thus the importance of LiveJournal's experience in scaling its architecture, which is based on Perl, as are TypePad and Movable Type.
A recent overview of LiveJournal's backend said it was serving 50 million pageviews a day from "100+" Linux servers running Apache. Even using the low-end figure of 860,000 weblogs updated weekly, that suggests thousands of active accounts per server.
Most hosting services allocate a set amount of disk storage space per account - TypePad, for example, offers 50MB of space with its $4.95 a month account. LiveJournal doesn't state bandwidth or storage minimums beyond a limit of 15 photos per account. That makes it possible to house a much larger number of accounts on each server than traditional hosting companies. In that environment, even a modest number of "free will" upgrades from free to paid LJ accounts will boost the bottom line.
Interesting view. I think the know-how of LJ will benefit Six Apart (the contrary with TypePad benefiting somehow to LJ would not surprise me, that would be a balanced win-win deal indeed). I just doubt it's the only driver, since the infrastructure costs of a hundred servers may not be the first budget line of the new company. It's key to have a highly efficient infrastructure though, especially when you support 96% of 2.5 million accounts for free!