The free package has a limit of 1GB (about 10,000 photos), and there is a limit on size (1024x768). You are limited to 30 images for slideshows and 5 minutes for video. There's also restrictions on copyright images and content (no porn), as well as a minimum age (14). And of course, no tech support. Otherwise load up the pics. They make their money through the Pro package and advertising.
If they weren't making money, they wouldn't be operational still. Don't worry about businesses, they're not worrying about you!