Am I right to be cautious?

I am a member of an online dating site . I often get obvious form responses from "women " encouraging me to check them out at an " adult personals" forum. It's , of course, spam. I now recognize the form letter and avoid. I have also gotten responses from women (nearly always an obviously professional photo of a strikng woman) who write in terrible broken english and use words that are just not right in context. They refer to a persons body as a "structure", etc. These I have found to be scams originating in africa, usually Nigeria. i don't open them anymore either. But I also get responses which are almost normal. The problem is they don't refer at all to what i wrote to them, nor use my name. They include a request to write to them on their personal mail address ( always yahoo or hotmail). Because of the vagueness in their notes to me, I somehow think something is amiss. I haven't responded to them. If i write to a yahoo/html addy, can they get my personal info, ID, or anything?