LEADING THE DAY: Sen. Chuck Grassley (R-Iowa) sent a letter to Federal Communications Commission Chairman Julius Genachowski criticizing the agency’s process in approving LightSquared’s satellite-based network, The Washington Post reported. In the letter, Grassley asked whether the agency had considered the cost involved in LightSquared’s request that military and other federal agencies retrofit their Global Positioning System technology to eliminate interference with the company’s proposed network.

The letter is just the latest example of Republican criticism of the way the agency handled the company’s request.

Calls for Facebook investigation: Lawmakers and privacy groups are calling for the Federal Trade Commission to investigate Facebook’s business practices, particularly how the company uses cookies to monitor users who have logged off of the site. Reps. Ed Markey (D-Mass.) and Joe Barton (R-Tex.) wrote a letter asking the FTC to investigate the company’s cookies Wednesday; on Thursday several prominent privacy groups followed up with their own letter to the commission, The Washington Post reported.

Facebook has said that it does use cookies that do not store unique identifying information, and that it uses the cookies for security — not advertising — purposes. Privacy advocates also asked the commission to investigate whether Facebook’s privacy policies adequately cover proposed changes to its site layout.

Spotify adds “private listening” option: Answering criticism from some of its users, the music streaming service Spotify has built in an option similar to “private browsing” that keeps the program from sharing updates on Facebook. “We’re rolling out a new client as we speak where you can temporarily hide your guilty pleasures,” wrote Spotify founder and CEO Daniel Ek in a Twitter message Thursday. Those who chose to link Spotify and Facebook were previously able to edit their sharing settings through Facebook; a Spotify account now requires users to have a Facebook account.

Tweet analysis reveals mood cycles: Researchers at Cornell University used Twitter to confirm some stereotypical expectations of how people’s moods change throughout the week, The Washington Post reported. Using two years of Twitter data from around the world, the researchers found that optimism is high at the start and end of the day and on weekends while everyone thinks Mondays are a pain.

Scott A. Golder, a doctoral candidate who worked on the study, said that the study shows that the data points to the fact that we are all “responding to the same biological rhythms.”

Amazon to buy Palm?: Amazon could be in the market for Palm, according to an anonymously sourced Friday report from VentureBeat’s Devindra Hardawar. According to the report, a “well-placed source” has said that the online retailer is the closest to finalizing a deal with HP for the Palm division. HP recently decided to stop producing Palm hardware, while Amazon jumped into the tablet market this week with a $199 device, the Kindle Fire.