Especially on unscripted shows, I regularly see logos on clothes taped over, signs blurred out, etc. Why? Surely they can’t be [successfully] sued for showing a company name or product logo in such a context. But I bet lawyers are involved somehow. What’s the deal?
My WAG would be so that they don’t show products that compete with those in the ads that might be included when that show airs.
They get paid by advertisers for product placement. If a brand name or logo appears in a show you can bet they almost certainly paid for it to be there. So it would be hard to sell those coveted product placement spots if other products were also showcased for free.
The law aside, brand management is a tricky business to negotiate through. Many companies are very image-conscious and want to control not just where their logos and products are shown, but also how they’re shown. Max Torque kinda touched on it in the linked thread. Another example might be a brewery or distillery not wanting its products associated with shows or movies that depict excessive or irresponsible alcohol use, or with celebrities who are known to behave like jerks when they get drunk. They don’t want their image tarnished by bad behavior, especially in situations when they can’t control how their logo is used. Some companies also take public stances on some issues and would certainly have problems with their logo or products being shown in situations that run counter to those stances; Chik-Fil-A would undoubtedly have problems with its logo or food being shown in a program that shows homosexuality or gay characters in a positive light because it’s a religiously-conservative company that is not known for being gay-friendly.
The other big issue is that companies don’t want to give anyone any ammunition that can be used against it. The aforementioned brewery may not want to deal with a boycott if some organization decides to make a point about irresponsible use of alcohol. Or a competitor may build a campaign around how its products are so much better because the people who use them aren’t skanks/douchebags/Guidos/hipsters/other negative stereotype, like Brand X’s stuff is. Companies want to avoid this wherever possible.
Essentially, what’s evolved is a sort of opt-in system where companies give permission for their logos to be used. Production companies may be well within their legal right to use them, but they do so at considerable risk, hence the blurring of logos.
Exactly didn’t your momma ever tell you a man don’t buy the cow if he’s getting the milk for free 
I’m bumping this, because Abercrombie & Fitch is paying Michael “The Situation” Sorrentino (of Jersey Shore fame) to stop wearing their clothes. I can’t make this shit up.