A post from LiveSide.net indicates that Windows Live Hotmail’s storage has gone to 500 GB in limit. I personally can’t imagine why you need that many unless if you are storing music files or whatever “backup” on your email inbox.
For example, I have about 13,000 emails on my Gmail account and it’s only using 388 MB at the moment. But hey, maybe if you are working in the design industry or in civil engineering, you probably need to transfer and store megabytes of file samples? Who knows. Anyway, it’s free and it doesn’t hurt to have more than you need.