What happens to online saves after PlayStation Plus expiration?
According to this press release, you will no longer be able to access your cloud saves if your Playstation Plus membership expires. However, your data will remain on Sony's servers for six months, and you can access them again as long as you resubscribe within that time period.
But, if your PS3 dies six months after you backed up your saved games, you've just lost 6 months of gaming! The way I see it, if you're going to back up your saved games at all, you should go the whole way and pay for PSN+ membership.
And you should anyway, since the cloud service is the only way you can backup your copy-protected saved games.
(Apparently the backup utility can backup protected saved games, but it can only restore them to the same PS3. If that PS3 is dead, then tough.)
According to http://uk.playstation.com/onlinestorage/, you can only access your online storage while you have a active membership. Once your membership expires, so does your access to your online game saves. Relevant excerpts are below:
If my PlayStation Plus membership expires, can I still use Online Storage?
If you stop your PlayStation Plus membership, you will not be able to access Online Storage.
Can I store copy-protected data using Online Storage?
If a developer has chosen to use the PlayStation 3 system saved data copy protection on their game saves, PS Plus members will still be able to save them with Online Storage and use them in the same way as other game saves. However, there will be a 24 hour period after saving before they can access the data on any PS3.