If I find something interesting, I usually don't even think about posting it, as I'm too lazy to check to see if it's a duplicate or not. Is there a cure for that problem (or my laziness)?
There is! If you submit a link that has already been submitted you'll just be sent to that post's page instead of posting a dupe.
This works, but not a perfect solution because the URL must be identical. For example if I post the link to the 'printable' version of a page this will not work if only the standard page has already been posted.