Why you shouldn't believe everything in the press

Not that I do, I'm a journalist after all.
Last weekend I got talking to a freelance journalist at a dinner party who has worked on the tabloids including a stint doing film reviews.
As an avid watcher of films I was fascinated by this and probably bombarded them with more questions than good etiquette would suggest.
Several interesting titbits of info came to light though.
The fact that some 'celebrity' reviewers from other publications got one of the office monkey's to go and watch the film and write up the review isn't surprising. Neither is the fact that reviews had to be tailored to the readership. Basically for this tabloid action movies all had to have high star ratings and if it was a remotely high-brow film or had subtitles then forget it.
However, when it came to films made by the newspaper's parent company the journalist was made to add stars to reviews if the original rating wasn't deemed high enough. Considering this company is a conglomerate with fingers in so many different media pies it does make you wonder how far this sort of interfering stretches. Would the same policy apply for the company's broadsheet papers for instance?
I've always believed reviews in the 'qualities' carry more weight but how can you be really sure that they are impartial?
And if one company is doing it, you can bet other companies are too. It is not enough, or financially viable, to be merely in the business of newspapers. Now there are films production companies, TV production companies, record labels, ISP's, radio stations, music festivals, mobile phones etc etc all from the same stables.
Obviously if someone wants to pay me to sit in a comfy private screening room two or three times a week, with a glass of wine, I'd write whatever they bloomin' wanted.