1GB Free (Paid plans up to 1TB; e.g. $5/20GB/year shared across Google services including Gmail)
Private URLs and limited settings control access. However, images may be indexed for Google Search and Google has a history of overstepping user privacy.
Relatively easy to use interface. Desktop client, batch uploading, integrated photo editing via Picnik, and other intuitive features typical of Google products make this easy to use.
Web, desktop (Windows and Mac), and mobile