I've seen a lot of people worried about why Owen and Beru didn't recognise R2-D2 and C-3PO in SW:ANH as being the same droids they'd met nigh on two decades earlier - eg, this most amusing article about continuity in SF films.
However.. perhaps I'm missing something, but why would they? As far as I can tell, R2-D2 and C-3PO are the names of models of droids, not the names of those individual droids. We see a lot of similar, if not exactly identical, astromech and protocol droids throughout the series. Why, then would Owen and Beru have any particular reason to think that one pair of droids is the same pair they met all those years ago?