I regret to say that I totally disagree with these practices and will explain why:
1. Those fans, even if they are not fake (I know some methods to get real fans and not directed for a very low price or even free, but still would not recommend anyone to do so), will affect you in a bad long-term path. Facebook already shows your posts at an average of 15% to 20% of your fans, alone and this is if you have any commitment on your page. If your followers are not targeted, your updates will be displayed at a maximum of 10% and, of course, you will not get any benefits from there. Therefore, it is possible that at some point you want to promote your publications and see them up to 50% of your fans and their friends. But, once again, you will not see any results, since they do not care about your business (many of them also "differ" from your page). Then, in the end, you'll have to pay more than if you were setting up a campaign to get specific fans.
Let's say that in a moment you will start to have specific followers, but most of your publications will not reach them due to the great majority that is not directed.
2. Regarding the large number of followers that will impress the visitors of your page, I think that, in this case, it is rather the other way around. Personally, I click on the Like tab when I get to a page that claims to have thousands of supporters. If all the "I like" came in a short period of time (a few days) it is obvious that they are false and therefore it must be the business. Also, it's OK to not have too much commitment on your page until you get 500-600 fans, but after that it seems a little strange and affects your credibility.
3. It is very likely that Facebook (and Google too) will penalize it if it gets followers tones from unreliable sources.
There are some more disadvantages I know that may occur because of this, but I hope you have already given enough information to support my point of view.