I gotta say though, even as someone who just freelances and hasn't been doing all that much work recently, this stuff makes me think about how I approach my job too. Which I think is the case for many journalists, which is a positive by definition.
Now, as mentioned on NMA, the only piece of swag I ever got for free as journalist (I've bough some paraphernalia off eBay) is a Fallout 3 T-Shirt, and I don't think it colored my perspective on the game much. I do get free games sometimes, and sometimes not. I'd be impressed by anyone who looks at GB's reviews and figures out which one is based on getting it for free, though maybe I should discuss with Buck again about showing an hour-log and free/not-free on reviews, I think I floated that idea before.
I think the biggest problem for me, personally, is just being a fan or hater of companies. I've always liked Piranha Bytes and their school of design, and I think I might've gone a bit too easy on Risen 2 as a result. I still think it's a decent/good game, but its flaws are rather significant, and definitely something they need to improve on for the next Gothic or Risen. Conversely, I might be too harsh on BioWare and Bethesda, just biased against them. Nothing wrong with having an opinion and tastes, but if you go too far in one direction of just not liking a genre (like I don't really like BioWare's games much) or of absolutely loving a genre too much, you might be best off avoiding reviewing them. I don't think I've ever reviewed an open-world TPS game (when writing for other sites than GB) and that's good, because I tend to love them always. Anyway, don't think it's been a huge problem for me since my review structure tends to be informative and explaining the reasoning indepth, so readers should be able to filter out taste. But still something to think about more than I have, when writing. Lesson to take on board!
Another thing I thought on was working for inXile. They don't pay me, obviously, though they might eventually compensate me for my work with some extra swag on top of my pledge. I'm kind of a community manager for the company, so I'm kind of invested in the title, and I think that shows in my forum posts on them. Not a problem, I think, as long as I just stick to forum posts. I decided ages ago not to preview or review Wasteland 2 for any site, GB and NMA both have better suited people for it. Still, good to think about it, even if it's an easily avoidable problem.
So uh...random rant!