[kelnos]

That's true, but absent psychological manipulation or something truly devious and nefarious, a short text message is low risk, and is unlikely to open up a painful can of worms.

And I don't think the point of that statement was that you should be contacting anyone and everyone, just because they entered your mind. It's not saying you should get in touch to say hello to that abusive ex just because you thought about them. But firing off a quick text to someone you found interesting but lost touch with is pretty much always going to be harmless.