The Boston Celtics are a constant source of rumors and speculation. They've been linked to anyone and everyone that's been theoretically available in the last few years. The most recent scuttlebutt has them linked to players like Russell Westbrook and Blake Griffin.
Let's make this clear: there's zero confirmation that there's actually been any serious discussion about trading Blake Griffin. The rumors started several days ago, and originated with smalltime bloggers and hack radio guys. If there was anything serious to it, you'd be hearing reputable sources talking about it (if not from newsbreakers like Adrian Wojnarowski or Marc Stein, then from trusted insiders like David Aldridge or Ken Berger).
These rumors fall into two categories. Most of them are the same outright speculation that we've seen with the Celtics time and time again, following the same script: Boston's chasing stars, Boston's got assets, wouldn't it make sense to trade for this guy? We saw it with DeMarcus Cousins, Jimmy Butler, Kevin Love, Jahlil Okafor, etc. We're seeing it with Westbrook now too — most recently from Howard Beck, citing speculation from "executives around the league." Ergo, no actual discussions or sources from Boston or OKC.
The rest are rumors or leaks from the Celtics. Note how reports almost always state that Boston is the team interested in trading for Star X. Of course Boston is interested, but that doesn't mean the other parties involved are taking their offers seriously. It's just like the rumors we've heard in years past about the Lakers being interested in LeBron or Durant or Westbrook or any other potentially available star.
We haven't even mentioned how ridiculous the offer supposedly on the table is for the Clippers. A three-team deal with Sacramento sending Rudy Gay to the Clippers? Why on earth would the Clippers ship out Blake Griffin for an older, worse player? No combination of role players or picks makes this a desirable or feasible trade for LA (and future picks do nothing for a team built around a 31-year-old Chris Paul, who might just bolt next summer without another superstar to play alongside in Los Angeles).
These are all based around the notions that the Clippers "have to blow it up", or that Doc Rivers is a terrible general manager who could easily be fleeced. No one from the Clippers camp has said anything to suggest that there have been serious trade talks (and Doc has repeatedly stated this offseason that he's not trading any of his stars, going so far as to pitch the idea of a "Big 4" to Kevin Durant).
Now that most free agents have signed with new teams, not much is going on around the league. It's probably not coincidental that these sorts of rumors, based on little more than flimsy speculation, are popping up now. Consider the sources and language of these reports, and whether they actually make sense for the players and teams involved. Usually, you'll find that they're nothing more than idle smoke.
EDIT: Here's a Celtics beat writer confirming just that — "Sources indicate the Celtics are very much open to major moves, but while situations certainly remain fluid and they have expressed interest in Blake Griffin and Russell Westbrook in the past, there have been no discussions regarding those players in quite some time."