From Greg:

There is a buddy limt, message limit (daily and monthly) and photo limit. All limits are in place to help control web server usage (ie: bandwidth, storage, processing, memory, etc.). Hosting a site like this is expensive...so I provide higher limits to members that pay to upgrade. But upgrading is not required...unless you need lots of buddies, or send lots of messages, or upload lots of photos.

Thank you! Greg.