Conclusion:
Flickr is a great place for your pictures, you can gain a great many good things from it including new friends! But… try to be a good community member. Be yourself, share your life, your process, and your work, but don’t spam. Enjoy it! It will widen your horizons and show you the most wonderful sights you’ve ever seen.
Whew! That is pretty comprehensive.
People should know though, that even if you set your photos so that no one can download and print them, they still can download and print them. It’s just a little more work but any photo from Flickr can be saved to someone else’s computer and printed. Their “spaceball” trick will only slow down a determined image thief, not prevent them.
If you really REALLY don’t want anyone saving your photos, it’s best not to put them online at all.