[spdustin]

Disallowing editing is only one solution I suggested. The other is: determining that they haven't actually changed the sample text from one of the pre-canned selections, and thus returning the result from a static copy of a previously-performed transformation.

Edit: in other words, if a user changes the text from one of the pre-filled selections (MD5 hash of the text would be sufficient to determine this, or even simpler, note whether a keyup event was raised by the textbox), put them in the queue you're using now. If there was no keyup event, then read which selection was made from the drop down and return the already-transformed-in-advance result.

Making a potential "ready to hear your pitch" customer wait in line is unnecessary. There can be an "express lane" without compromising the "scenic route".