DOJ e-book case: Barnes & Noble filed a complaint Thursday siding with Apple and book publishers in the antitrust case over e-book price-fixing.

Reuters reported that the mega-bookstore said that the government’s proposed settlement is bad for consumers because it will give Amazon too much control over the e-book market. The report said that Barnes & Noble claims the proposed settlement would lead to less consumer choice and higher e-book and hardback prices.

In April, the Justice Department sued Apple and five publishers, three of whom settled with the agency, alleging that the companies had colluded to fix book prices.

Patents: A judge in Chicago canceled a jury trial between Apple and Motorola on Thursday, saying that the two companies sparring over smartphones can’t prove that they are entitled to relief.

As patent blogger Florian Mueller noted, Judge Richard Posner had previously dismissed both companies’ claims and that it’s “likely” that the case will head to the federal circuit. The case was over four Apple patents and one patent from Motorola. Google’s $12.5 billion takeover of Motorola was finalized last month.

Apple expands prepaid: Customers looking for Apple’s iPhone on a month-to-month basis got another choice Thursday as Sprint’s Virgin Mobile announced it would offer the phone, starting with a $30-per-month plan. The carrier will throttle data after 2.5 GB of monthly use.

The cost of the phone itself is barely subsidized but is likely to appeal to those who don’t wish to sign up for the two-year contract offered by postpaid carriers. Cricket, a subsidiary of Leap, also offers a prepaid iPhone with a $55-per-month data plan.

Facebook App Center: Facebook, looking to plug its mobile gap, has unveiled its app center, which offers the company another potential source of revenue. The news comes just a day after the company explained its new mobile payments system, a two-step process that charges money to a users’ mobile phone account.

Meanwhile, the Wall Street Journal reported that NasdaqOMX Chief Executive Robert Greifeld faced questions from those who said that compensating firms for the money lost in Facebook’s glitch-plagued IPO was not the way to go.

Other exchanges are also not happy with Nasdaq’s planned $40 million payment to firms. On Wednesday, NYSE Euronext issued a statement saying it thinks such a plan would be “wholly inconsistent with fair practice and an undue burden on competition” and would be “tantamount to forcing the industry to subsidize NASDAQ’s missteps and would establish a harmful precedent that could have far-reaching implications for the markets, investors and the public interest.”