With Google's recently released GData API for Google Base (see the ProgrammableWeb API database entry here), there is renewed debate on their grand strategy. Is it a better mousetrap? Lock-in? Neither? For good commentary see these posts from Marc Canter and Chris Messina (with lots of trackbacks from there leading to more discussion). In the end this question may apply to all the big providers. We'll see soon enough.
Speaking of Marc's blog, he also had an interesting series of posts about Facebook's API.