My bloggers have several non-standard plugins and non-standard theme tweaks.
Edit: and oh yes, 2.5Gb of media.
The big kicker is that my migrations can only occur by SQL. Using WXR is fine for any blog that can be turned from XML into PHP objects ... inside the execution-time limit.
Otherwise Wordpress thinks it's just hilarious to silently fail to import anything that doesn't make the execution-time cutoff.
And I don't think I am a big enough fish for wordpress.com to bother to help me do an SQL migration.
Put simply: cost. Collectively it's a few hundred Gb per month of traffic which is completely covered by my Linode plan.
These days I've put most of the sites behind Cloudflare, which has the effect that a lot of my media is being mirrored in their Sydney DC, which is nice because most of the readership is Australian -- the same reason I went to the Tokyo centre this time.
The Tokyo DC isn't a universal win for Australia. The results are actually pretty bimodal depending on your ISP.
From Perth, iiNet routes directly to Asia, and it's a big win. But Amnet routes AU -> US -> Asia and it's a big loss.
It's a big enough issue Australia-wide that Blizzard sells a dual-region Starcraft 2 in Australia, because (ping to battle.net Singapore for some) > (ping to battle.net US) > (ping to battle.net Singapore for others) to a significant degree.
Not really. WordPress.com's free hosting has limited space, no custom themes, no plugins except a small preapproved set, no ability to run your own ads, and you have to run WordPress's ads for their benefit.
You get a little more storage space, a little bit of CSS control, but you still can't bring your own themes and plugins, edit the code, etc. Plus, there's no way to migrate a multi-gigabyte blog network's data over, AFAIK.
WordPress.com is an SaaS for blogging like Tumblr or Posterous. It happens to be built on a custom, locked down install of the WordPress multi-site software. It's not a website hosting company.
Edit: and oh yes, 2.5Gb of media.
The big kicker is that my migrations can only occur by SQL. Using WXR is fine for any blog that can be turned from XML into PHP objects ... inside the execution-time limit.
Otherwise Wordpress thinks it's just hilarious to silently fail to import anything that doesn't make the execution-time cutoff.
And I don't think I am a big enough fish for wordpress.com to bother to help me do an SQL migration.