Prior to meeting someone on CM, I received a few messages from women. Here is my two cents...
I always replied, but....
If all I got was an emoticon, I usually only replied back with a very short one line message...if the woman was not willing to write a sentence or two indicating what she liked in my profile, I figured we were not going to be a good fit...too timid and unsure of herself.
If all I got was a one line message that was generic, as in "Have a nice day..", then see above...too timid. I want to know what you saw in me that made you contact me.
If I got a long rambling message that was mostly focused on you rather than me, I would also reply with only a short note. I'm not interested in women who think they are way more important than me. Tell me a little about yourself, but a half page letter about your bad day at work is not a good way to get me to respond with much more than "thanks for writing."
If I got a brief, three or four sentence note that mentions a couple of things that you liked in my profile, now you have my interest. You have shown me you actually read my profile, you found something you liked, you told me about it, and now the ball is my court. And if I got this kind of note, I usually wrote back with a similar note.
And if you wrote a brief note about what you liked in my profile, AND you asked me just one question that invites me to respond, now we have a conversation starting up.
...and that is how I first became interested in the woman I met here...she wrote to me, she mentioned some things she liked in my profile, and she asked me a question about where I grew up. I wrote back, answering the question, and off we went!