Every single review site and retailer faces the same exact dilemma which is why using common sense and good judgement is important. However, here there are many things preventing sources from doing this.

1. It takes 6+ months to become a Verified source which is very valuable. Fuck up and they lose that and will be banned.

2. Mods are monitoring the review section for exactly that, multiple accounts, and have additional functionality to research. Review the forum post my profile for an example.

Regarding getting in touch with Admin... you are better off contacting a Mod.

We are big boys and take risks with this for new guys like myself and many other there will be a lot of trial and error for products I'm not saying doases and stuff like that but what brands work the best for everyone. There couple be a line that works for 98% top notch but the next guy it might not and they might think the line is bunk and it's all fake reviews. Everyone is just different. Over time you will find for yourself what you think is best the reviews and votes are to help guide not a for sure.

All the new members voting or 1 karma members make me question this as well...
Use your own judgement and if you see someone like PMOB here voting, its most likely a source to consider-

This is an easy question. "Mods" everything is over seen. It's easy to create multiple accounts yes but I.P's and vote's don't lie. There's a lot that members don't see in the backgrounds of this site. Mods are on top of every click we take.