It's true that Reddit's filter is hard to bypass, but it's not impossible and a lot of businesses and marketers are taking advantage of that.
First of all - the guys from above are right - Reddit's Filter Algorithm is brutal. If you are not super-careful you are going to get filtered and you won't even notice that. As noted above, there are at least a couple of important factors when upvoting that might get your posts automatically filtered and your site/account shadow-banned:
1. Posting links regularly to less-known sites
2. Using multiple users from the same IP
3. Posting/upvoting/downvoting from new accounts
4. Posting/upvoting/downvoting from accounts with low link and/or comment karma
5. Posting from different IPs
6. Doing any suspicious patterns like only upvoting and not commenting or posting links at all
7. Using automated voting bots (seriously, just forget about that...)
etc.
You need to have a lot of time and money to invest in real accounts with karma, proxies and VPNs.
I'm the owner of a site called Reddit Secrets that specializes in upvotes ( redditsecrets.Ñ0m/buy-reddit-upvotes ) and I've been doing that for some time.
It's hard. But it can be done. I guarantee you that, and the results are worth it.