Some times it is the only option for some people, depending on where they live and if they don't have time, money, or the opportunity to travel to larger areas where bars, clubs, or other activities are held. Not every community has a gay bar, not every community has a gay friendly church, not every community has a gay club for everything under the sun. If you can't travel to places that do offer those things, then where are you left at?
In creating a profile on any site, be truthful about yourself, let the other guy do the deceiting, explain what you are looking for upfront with clear, concise language (this way you aren't leading anyone on), and be careful of what you say in responses and DO NOT share any personal or private information with anyone until you have actaully seen, talked with, and decided on. DO NOT share addresses, land line phone numbers, last names and such as people can track you down. Do not offer assistance to other people. If you are meeting someone, always meet in person at a public place where there are always other people around, let someone you know and trust know where you are meeting a person at, and NEVER do something that you are not comfortable doing. DO NOT let someone talk you into doing something that you don't want to do or are not comfortable doing. The word NO still means NO.
There will be a lot of game players, scammers, freaks, and worthless trash out there who will contact you. You will know how to read them, gets better with practice, after some exchanges with them. Don't go off and meet someone after the first email. Talk to them, get to know them, find out what they like to do, what they are interested in, talk about life, experiences, goals, and the like. As you are doing that you will be able to tell if they have their heads screwed on right and if they are really truly interested in meeting you for a person or if they are just looking for a quick roll in the hay. Also, the more you can communicate with someone before meeting, you will be able to tell if they really are interested in you as a person or if they just want another conquest. Also, be aware of what they are saying in each of their messages and look for inconsistencies in what they say about themselves. If their stories change from message to message, most likely they are a gamer and can't keep their stories straight and then it is time to cease and desist with them and avoid any further contact.
And don't worry if your guard lets you down and you screw up. We have all been suckered at least once by someone who we thought was nice, really into us, and who was the one we were looking for. Fall down, get bruised, get hurt, and then learn from it for the next time so that we grow and won't let it happen to us again.