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.