Dating through agencies in Spain is as popular as anywhere else and many people find this the best way to make new friends, not always for long-term relationships but for company. Dating agencies in Spain are regulated and reasonably safe. It is common to find a partner online in Spain but the usual precautions should be observes, such as not giving out your personal details until you are 100% happy about the possible partner.
There are many people in Spain that met their partners online and have managed to form perfectly healthy, long-term relationships. If you are in any doubts that it is for you, try it.... you have very little to lose.