Every major news outlet and most minor ones have reported that the husband and wife team of terrorists in San Bernardino "declared support for ISIS" on social media sites before engaging in the attack. This feeds smoothly into the narrative of a terrorist attack, but it misses the point of what, if anything, posting something on Facebook and its equivalents proves.
There is a useful distinction, obliterated in practice, between declaring support for ISIS and being affiliated with, or in some way receiving support from, ISIS. Logically, anyone with internet access can throw up a post saying, "Wooooooo ISIS #1 ruuuuuuuulez!" in the moments before they engage in activities they do not expect to survive. Other equally useful declarations could be "Hail Satan!" or "J-E-T-S, JETS JETS JETS!" On the other hand, being in contact with and receiving necessary information or equipment from ISIS would be a different and more meaningful story.
For years during the Bush administration I asked, whenever they crowed that their policies had stopped another terrorist attack in preparation, what "in preparation" meant and whether the plot had any realistic potential to be executed. In fact, it often turned out that the only thing keeping these one-lung plots afloat was an undercover law enforcement officer offering to provide hard-to-get materials. Is it a good thing that someone plotting a terrorist attack is interrupted in progress? Of course. But there is a relevant difference between a well funded, well organized, realistic plot that could have proceeded to completion without the intercession of law enforcement and a bunch of jackasses who couldn't successfully execute a liquor store robbery sitting around googling "how to make terorist bomb" and publicly available schematics of famous buildings. Presenting both categories as equals is misleading at best, deceptive at worst.
The FBI director has stated that the San Bernardino attacks were "inspired by" foreign terrorist organizations. Tellingly, that is the same phrase movies use when they have only the most superficial relationship to source material. "ISIS operatives" and "copycats/wannabe terrorists" are two distinctly different things and, as usual, the distinction is absent.