An amicus brief filed by the EFF suggests that Atlantic is suing Pamela and Jeffrey Howell based on attempted, rather than actual, infringement and that there is no evidence of infringement other than hearsay evidence by Atlantic's hired investigator (MediaSentry).
Here's en excerpt from the brief:
Plaintiffs' investigator, MediaSentry, did not observe Defendant's disseminating any materials to third parties. Nor do Plaintiffs contend that MediaSentry invited Defendants to make any unauthorized reproductions. Nor have Plaintiffs established that MediaSentry's downloads constitute circumstantial evidence that the Howell's computer disseminated copies of the 11 songs in question to any other KaZaA user. In fact, Plaintiffs' own evidence makes this seem particularly unlikely. According to Plaintiffs' expert, during the period that MediaSentry performed its investigation, there were 2,282,954 KaZaA users online, sharing 292,532,420 files. . . . Even accepting Plaintiffs' hearsay testimony as true, these facts together suggest that it is highly unlikely that, among the millions of KaZaA users who are likely to be sharing them at any time, these 11 songs would have been downloaded from Defendants' computer. At any instant, KaZaA users are likely to have thousands of sources for these particular songs to choose from and no reason to choose the Defendants' computer over any other. And while Plaintiffs may be correct that, in the aggregate, KaZaA users engage in a prodigious amount of infringing activity, that general statement tells us nothing about the crucial issue in this case: whether these Defendants transmitted (i.e., uploaded) any of these 11 songs during the time period in question.
Here's an excerpt from "EFF Files Brief in Atlantic v. Howell Resisting RIAA's 'Attempted Distribution' Theory":
As in more than 20,000 other lawsuits, the recording industry claims that Mr. and Mrs. Howell committed copyright infringement by using P2P file sharing software (in this case, Kazaa). But rather than going to the trouble of proving that the Howells made any infringing copies (by ripping CDs or downloading songs) or any infringing distributions (by uploading to other Kazaa users), the record labels argue that simply having a song in a shared folder, even if no one ever downloaded it from you (i.e., "making available"), infringes the distribution right. This essentially amounts to suing someone for attempted distribution, something the Copyright Act has never recognized (although the DoJ unsuccessfully tried to get something like that from Congress last year).