I’ve posted my answer there - you have to scroll a bit to get to it. I am reposting below as well - just in case you miss it.
Here we go:
I’ll start by saying that I’ve generally found both of these services reliable. But let me explain the approach required to getting the most out of these platforms. There’s no free lunch - read on.
As mentioned by many in this thread, the sites provide a meeting place, or an exchange where freelancers and those seeking work meet. The sites function as an intermediary and don’t guarantee the work, the quality, its timeliness, or the ability of the parties to find an agreeable price. They provide the infrastructure.
As with anything else, work on your part is required. There are meaningful friction costs involved in hiring, managing, paying, and auditing freelancers. Just like a regular in-house team, you need to pick the people, define goal, set milestones, and agree on terms of reference and budget.
The garbage-in-garbage-out problem is pervasive. The initial investment of time and resources is where most people stumble. It’s not sufficient to just hop on and request that someone builds you a website with the functionality of Facebook. You need invest the time to break down your job into discrete, manageable pieces, provide pseudo code or extensive detail of resources, where necessary, really think about how you would brief a newly hired internal employee on a project.
When you post a job, make sure you search for similar jobs and find qualified, highly rated contractors that have done similar work. Invite them for your job. I’ve found that this sometimes works better than just doing a public posting.
Once you have a core group that you’ve invited, look at their proposals and pricing. You will find that most of them will be in a fairly narrow range, regardless of their location. Exclude the outliers - those high and low, and then engage directly via the platform or skype with the remaining few. Interview them to understand their time constraints, capacity, whether they work alone or if they are an English-speaking “dispatcher” for a group of locals.
Only once you’ve done this work do you stand a chance of getting a quality product. Throwing something at the wall, as in real life, will be a waste of time and money.
The big benefit of this process is the hope that because these freelancers are specialists, and because their implied pay rate is theoretically lower than hiring a local or a full time employee, the overall project cost and completion time will be less. Most of the time it does work out that way.
Once the job starts, it should be broken down into clear milestones where you can check the quality of work done to date and course-correct if needed.
Over time you will build your core team of freelancers on these sites and will grow to rely on them. Overall, these sites provide a tremendous productivity tool.
Now, the above is applicable to complex, multi-step projects that require extensive interaction and continuous engagement. If your task is discrete, well defined, quantifiable and “qualifiable”, there are a emerging platforms that are willing to be the intermediaries in the process and take responsibility for the quality of the end product. www.ziptask.com is one of these.
To do this, they use a combination of human capital and IP to assess the task when it comes in (make sure the instructions are clear and have all conditions necessary and sufficient for it to be a success), use a smart queue system to assign the work to the most qualified contractor available and on-line at the time, and then sanity-check the work when it comes in. Because humans are added to the process, the results tend to be of higher quality, and poor work does not go back to the client. Because the tasks are done by hyper-specialized providers available in real time, they are done quickly and inexpensively.
These types of services work best with MS Office, graphics, research, and other simple or digital tasks, (examples here: https://www.ziptask.com/pages/zAboutExamples.aspx )but again, providing clear definition of the work is key.