Never mind grandpa
I reckon an ebay account would be useful, you can still get ripped off but not as easily as you could in its early days. Most of the time it's just using your noddle, checking people's feedback scores etc.
Facebook, meh, I had one account but it started getting filled up with what people had for dinner, football, stupid games, lots of nonsense I really wasn't interested in, so rather than offend people by telling them to eff off, I killed the whole thing and started again. This time round I'm trying to be more selective in who I "friend": so far I have one
This was the first time I'd uploaded anything to twopubes, a mate of mine has loads of stuff on there (I'd link some but he seems to have made it invisible somehow, so I reckon he wouldn't want it slastered across the interweb here). I guess if you filmed something you'd like us to see you'd figure it out, otherwise I wouldn't include it on your list of things to do before you die...
I've never had a twitter account and I'm sure there's loads of other sh*t out there that wouldn't improve my life in any way, shape or form, I wouldn't loose any sleep over it anyway.