A friend of mine recently forwarded me a newspaper article about a land developer that was doing work on lands held by the Bureau of Land Management, and the BLM had bowed to political pressure and this developer had been "allowed" to hire their own company to do the environmental impact report. She was livid that the BLM was making an exception for this company and allowing it to hire the people who would determine whether or not the company's activities would have negative environmental impacts.
You can only imagine her reaction when I informed her that the BLM was not bowing to political pressure, that project proponents (that is, the people or organizations wanting to do a land development project) typically hire their own consultants to to the environmental impact statements (in fact, that's a primary reason why companies such as mine exist), and that this was not a case of a large company getting something special because of political ties, but rather was simply the normal mechanics of how a land development project proceeds.
This does, admittedly, sound pretty bad. Even when nothing nefarious is going on (and after many years experience in this field, I have learned that things are usually on the up and up), the fact that the people performing the environmental analysis for a project were hired by the people who want the project to go through does look pretty...well, strange. There are three things that one should know about this, however.
The first is that those of us who do the environmental work are consultants to, and not employees of, the proponents. This may seem like a fine distinction, but it is actually quite important. We are expected to understand the relevant laws and regulations, and to explain to our clients how they have to behave to keep in compliance with them. If the regulations say that "activity X must be proceeded by precaution Y" then we explain this to our clients. Our environmental review documents are just as much prescriptive ("in order to avoid impacts, the project proponent must take these precautions...") as descriptive (simply describing the environmental impacts of a project). Now, that's not to say that there isn't room for corruption in the system, there certainly is (and I know of a few archaeologists who I suspect are on the take, based on some of the results that they have put into reports), but it does mean that we don't have the same pressures on us that a direct employee of the company would. So, yes, there is room for corruption, and the fact that a project proponent is paying for the environmental review does look rather off, but it should be understood that the purpose of the environmental review process is to document potential problems, relevant regulations, and define the terms under which problems will be avoided or mitigated, not simply to give a thumbs up or thumbs down to the potential for a project to have environmental impacts.
The second thing is that these reviews are not done in a vacuum. As part of the review process, stakeholders must be identified - community groups, Native American organizations, individuals whose homes or property might be impacted by the project, historic societies, recreation groups that make use of an area, etc. The outreach to these groups can be done poorly, and often has been, but it is something that is part of the environmental review process. When you hear about how a project was halted because of environmental concerns, it's usually because one of these stakeholders (or somebody who should have been identified as a stakeholder) has terminated consultation and is seeking legal action. Identified stakeholders are given the ability to review documents, to ask questions, and to provide comments that can (and often do) result in further review or mitigation work being done. In other words, just because a large company hires the consultant to do the environmental review doesn't mean that the documents stay between the consultant and their client, they are reviewed by stakeholders, and often put out for broad public review, in order to allow for comments to be received regarding the level of effort, and anything that might have been missed (or excluded) by the consultant who prepared the document.
The third thing that should be kept in mind is that this review process is not unsupervised. All documents must be received and reviewed by the government agency that is providing the permits/money/donkey rides/whatever that the project proponent needs. Normally the documents are reviewed by a specialist at the agency (so, an archaeologist who works at the agency will review all archaeology materials, a biologist all biology reports, etc.), and the agency must sign off on the report before it is finalized. In some cases, the agency may hire a consultant of their own to help with this oversight, which often results in a rival company overseeing the work of the other - having been on both sides of this, I can tell you from experience that it does lead to a heightened sense of responsibility on the part of the proponent's contractor. Consultants who have a tendency towards corruption tend to draw the attention of the federal agencies, and there have been cases of people being pushed out because of this (probably not as many cases as there should be, but still), so most consultants feel a stronger need to keep on the good side of the federal regulators than to keep on the good side of any one client.
Now, there has been talk of ways of reforming this system, such as the proponent paying a fee to the agency and the government agency hiring the consultant who does the review, to remove the appearance of subservience to the proponent. These sorts of solutions all have problems of their own, but I appreciate the notion behind them. Regardless, the system, as it exists, is not simply a matter of "proponent hires consultant to say what proponent wishes" - the system is more complicated. Not to say that there isn't room for vast improvement, but it's not the horrific mess that many people seem to feel.