Hi Wayne,
Sorry for the delay, but I wanted to give it a little more thought.
I assume you are asking about being "picked off" ???

I have seen enough references/comments on the practice, but in truth, have never seen anything on just how it might work. I have always assumed there was something like the NASDQ Level II bid/ask queue where I understand that queued orders are visible to "some". Just who, I do not know.

Will come back to the above in another post as well as the Icd post comments on HFT and Ng.

On Bobs comment: I'm sure the poker analogy made sense, you are exposing your intentions to the exchange/marketplace, but I'm not completely sure just how the process might work to their advantage ??
Anyway, to your direct question, I have always avoided the issue since OptionsXpress offers "conditional orders" that are not sent to the exchange until the "conditions are met". The order is stored on the Ox computers and continuously examined. When the criteria is met the order is sent to the exchange. This may sound "messy/slow" but it happens in milliseconds, much faster than you could make a mouse click !!!!

Now, there are some issues though ........
There are 2 basic order types:
A Trailing stop and an ATO (Alert Triggered Order) each has advantages and disadvantages, and either can be specified to become a "market order when triggered" OR a Limit order when triggered.

Use of Market orders exposes you to "fat finger" transients and Limit orders if (poorly placed) exposes you to being "skipped over". Either could/should be the subject of another discussion.
[I always use Limit Orders]

A trailing stop is nice BUTTTT if the market is moving in your favor the stop trigger keeps moving up/dn and eventually you can/will slide into an S/R area and your trigger will wind up right on the S/R line with some attendant price volatility and unless your stop is "wide enough" you will likely be stopped out. Also, the Limit price is established when you place the order, so can get quite far from the final trigger price (same exists for the ATO order). All you have to do is periodically modify your order, changing the limit .... If you are so Lucky to get that far ahead !!!!

The ATO is similar in most respects except that you specify the trigger and it is fixed. Avoids the sliding into a volitile area. If you are Lucky, all you have to do is adjust the trigger price periodically.
And again, stay clear of S/R levels!!!

Sorry this got long, but maybe it will trigger some further discussion.

Lee