Online dating is nothing more than a "tool" to meet other singles. Just like a fork can be used to eat a garden salad or a slice of double fudge.To blame online dating for having a bad dating experience is equivalent to an obese person blaming their knife and fork!
It always comes down to the choices the (individual) makes. Out of the thousands of profiles out there (they) chose whomever they wanted to go out. The Internet did not invent liars, cheaters, or conmen. The same people online also are in the grocery store, malls, colleges, on the train/bus, and even in church. It's not where you meet but whom you meet that counts!
One of the main mistakes people make with online dating is believing all of the dating sites are about the same. That's like saying staying in a Holiday Inn hotel is the same as staying in a Ritz Carlton Hotel simply because they both have TVs and beds! It's pays to do research before selecting an online dating site. You have to know what (you) are looking for. Before you meet you can use Skype or Google Hangouts to see each other if you have concerns over whether or not they look like their photo.
Also worth noting there are many "niche" dating sites where people can get together who have a (strong) requirement for any future mate such as religion, race, age, or a hobby/lifestyle that is important. I've seen sites like MustLovePets.com, Alikewise.com (book lovers), VeggieDate.org and so on. My point is there are thousands of online dating sites to consider. I generally recommend avoiding the "free sites" as they're likely to offer a lower "quality" of prospects.
Having said that it's important to use good common sense when communicating with strangers online or offline. Use the website's system to contact one another until you feel comfortable to exchange personal email addresses and phone numbers. Always make the first date a lunch date where you (meet) at a place you're familiar with.
Lastly I would say online dating is probably best for people in their 30s and beyond if they are looking to "settle down". It's pretty much unrealistic for a woman in her 20s to expect a guy in his 20s to be ready to settle down.