Maybe you'd like to put your trades and trading life on display: Maybe you want to feel yourself to be part of a community. Maybe you like the idea of others admiring your success. Quite possibly, you believe that exposing your trading rationales and results to a small "public" will reinforce your own learning process and discipline. You may also hope that criticism or other commentary might show you some useful or interesting things you might not otherwise have considered.
Unfortunately, you can't get those or probably any other benefits from keeping a journal unless you offer something: Enough so that comments and criticisms have some meaningful context and points of reference, and also enough so that anyone might have good reason to follow along, if only passively. The less you offer, the less meaningful whatever exchange, whether real or imaginary, can be.
It's possible that the widespread worry over giving "trade secrets" away is highly overdone in these parts, and amounts to paranoia, and that, except perhaps in some very narrow instances, it's rather highly unlikely that a set-up, pattern, approach, or idea will lose effectiveness as a result of having been outlined in an ET journal - even a relatively popular one. If that's true at all, then the real question is whether you feel that what you'd get out of doing a journal, as above, is enough a) to make you feel comfortable casting your "pearls" before us swine - and this site can be, in my observation, rather a swiney affair, on the whole, and b) worth the intrinsic effort.
As for myself as a reader and ET member, I have yet to find any journal very interesting for longer than a few pages - precisely because the writers seem generally so reluctant to reveal much about what they're doing in any accessible way: Mere lists of a day's trades hold close to zero interest for me. I've occasionally been sustained by a bit of personal drama - trader contending with the effects of account disaster, that kind of thing - but I haven't seen anyone take it very far, and don't really expect anyone to do so.