Recently, Dropbox the popular cloud-storage company doubled the amount of free space you got for inviting friends to Dropbox. How much is that? For every friend you’d invite who installed Dropbox, you’d both get 500 more MBs of free space. With a free account, you can invite up to 32 people for a grand total of 16 GB of extra space. Pro, read paid, accounts now earn 1 GB per referral, for a total of 32 GB of extra space. Better still, you get this space retroactively if you’d already gotten people to give Dropbox a try.

That’s great, but does it make Dropbox the best of the personal cloud storage services? Maybe. Everyone, and I mean everyone, is offering some kind of infrastructure as a service (IaaS) cloud services lately. In IaaS that you find file storage, ala Dropbox, but other companies like Apple, Google and Microsoft are also offering storage, media serving, and other IaaS ad hoc services for either free or minimal prices.

The six best personal cloud storage options (gallery)

These services are transforming rapidly. Prices, amounts of free storage, and additional services beyond pure storage are constantly being changed. Here’s what’s what with them though in the spring of 2012.

The six best personal cloud storage choices for your stuff. More >