Worth mentioning also is that you should take care to set relevant privacy settings on anything you post online. Picasa, Flickr, Facebook, all the major ones have privacy options.
In the case of Flickr, you can set your albums (some or all) as Private, which makes them only 'generally' accessible to your Flickr contacts, with the added ability to send anyone an link to a specific album (say, by email), and they will be able to use that special link to access that particular album without a password (you can also 'cancel' a link from working if it gets publicised, if need be).
In Facebook, you will usually want to set most family albums/photos to "Friends Only", while it's easy to set "Friends of Friends" for more general stuff like funny shared pics. Considering that many people on Facebook have upwards of even 1000 so-called 'friends' (!), it pays to be a bit discriminating with the FoF option.

You can change your default setting for new posts/uploads in Facebook's Privacy Settings page, which can be accessed by clicking the arrow next to the Log Out link up at the top right. You can choose to make a new post, photo or album "Public", "Friends of Friends", or more restricted to only a few people you choose from your friends list, by clicking the little padlock or gear symbol on any new post.
Picasa Web Albums used to be pretty lax with their privacy options, only providing an 'Unlisted' option (not very secure), but they improved things sometime in the past few years and this page from them gives a simple explanation of their current options:
http://support.google.com/picasa/bin/answer.py?hl=en&answer=39551
Finally, you should always ensure you have an offline copy of all your precious memories, as companies do shut down or discontinue services, web servers can fail, get damaged or hacked, or people can make mistakes and lose files as a result. External USB hard drives get cheaper by the month (despite the November 2011 Thailand floods sending prices skyrocketing due to factory shutdowns/damage), Officeworks.com.au currently have a Seagate 320GB Pocket Hard Drive @ $55 on a promotion, or you can pick up a 16GB USB key for around $20-25 (32GB about $35) if you want something small enough for your keyring.
It's worth it, to keep your memories safe!
Kind regards,
- Matthew
Please note: I do provide data recovery services along with my regular business of computer repairs, and at much, MUCH better value than commercial data recovery companies (I've seen many cases of those essentially holding customers' data for ransom, and almost always 4-figure bills, ugh.) Please feel free to contact me (Matthew, Techie Matt) on 07) 5641 4666 if you're seeking advice regarding a related problem. I hope it's okay for me to include this
