The FTC has decided to look into some past acquisitions made by Google, Amazon, Apple, Facebook, and Microsoft, going back to 2010, asking them now to provide information that wasn't previously required under existing anti-trust regulations. The Commission claims it wants to deepen its understanding of these sorts of smaller acquisitions to better determine if they could be preventing competition in previously unanticipated ways, though it doesn't currently claim any of the companies involved were engaging in anti-competitive behavior.
As part of the announcement, the FTC cites its ability "to conduct wide-ranging studies that do not have a specific law enforcement purpose," meaning it has the authority to look into these details without pinpointing a specific reason, engaging in the sort of oversight the commission is supposed to when it's curious about something.
The focus of this not-quite-investigation is an undefined set of acquisitions made by the five companies that were all too far below the HSR Act's thresholds for reporting, and to help it learn more about these smaller acquisitions, partially to determine if some of them may actually be a detriment to competition, even if they aren't covered by current restrictions.
Orders have been issued to the companies in question, presumably including more specific details such as new thresholds for reporting or any specific acquisitions the FTC wants information about. Eventually, information garnered from this study could result in additional restrictions regarding future acquisitions.