I don't get paid to do them. I do however get to keep the gear in most cases.
In my case I kinda fell into it. I joined HWC in its infancy, and over a period of time was invited to take on a moderators position on the site.
As the site caught on, manufacturers started offering us gear to do reviews on (cheap advertising for them if they get a half decent review out of it). I got a few smaller items to do, and did quite a few for the site on gear that I'd bought myself.
As it stands, I'm mostly out of the reviewing buisiness for now as I just don't have the time to devote to them. Take this last review as an example... simple case review right???
6 - 8 hours putting all the gear together and making notes on pros/cons of the case, 4 hours setting up and taking pictures (all of the non-install photos were done for me already), 4-5 hours benching for temps, and probably about 30 hours writing and editing the actual review.
Add all that up and you're looking at a full weeks worth of work for whatever the value of the item is. In the case of a higher end motherboard or case, it's nice to have the item at the end, but the same kind of work goes into reviews of smaller items like cpu coolers, or HDD enclosures so in the end it's really a labour of love rather than an attempt to make any coin, or even pick up free gear. This is especially true when you consider that we risk damaging our own gear during the review process, and also need to keep our cpus/mem upgraded to keep up with the stuff we're reviewing.
Hopefully this doesn't sound like I'm complaining... I love getting new gear to test out, and enjoy the process when I have the time to do it. Just wanted to put the point across that the review process isn't all wine and roses.
If you're truly interested in being a reviewer, the best advice I can give is to do "members reviews" on the sites that you frequent. At HWC we've invited a few of the members to become official reviewers based on those, and recently held a "members reviews" contest where we picked our two favorite to become official reviewers.
Returning to your actual question about being paid.....
I wouldn't trust any site where the reviewers were being paid by the manufacturer to do reviews, and unless it's a magazine with professional writers, would also question the bias of those paid by their websites to do reviews. (I'm not saying for sure that they'd be biased, just that they'd have to go a long way to earn my trust).