Okay. I can see how that came across as kind of harsh. And it was in no way meant as an attack. But I have a major problem with these crowd-sourcing websites, in that they essentially exploit free labor and, in general, you don't get paid anywhere close to market value — and a lot of young designers aren't aware of that.
There are numerous ways to build up a portfolio that won't result in you providing free work for a client. There are exercise books (which you could probably get from a library) that have faux-creative briefs in them. That's a great place to start. Beyond that, you can even donate your time to a non-profit organization and get the tax writeoff. Your portfolio doesn't need to consist of work you've done for actual living, breathing clients. It can have doodles or personal projects. Most employers are more concerned with the way you think and the way you approach a problem.
I'll try to find the name of some of those logo-exercise books in a bit.
Here's a site that better explains my position on spec work.
The analogy I like to use is this - you don't go to 25 different restaurants, order food, and only pay for the entrée that you like. So why should it be any different with design work?