Why is this important? Well, I discussed the impact of these buttons (which can be severe or negligible, depending on certain factors) in a blog entry I wrote back in 2007 when CF8 was released.
And today someone was kind enough to point it out to someone on Twitter, so I took a look at it and tweaked it a bit to give some more context. While doing that, I realized I'd never mentioned this fact about the "start" buttons, and about an important related change in CF 9.01 (and 10), thus this entry.
The buttons remain enabled over CF restart or closing the monitor
So the first key point, when someone appreciates the potential negative that the buttons COULD have (see the other blog entry--they don't t always have negative impact) is that someone may not realize that turning them on and then closing the monitor doesn't eliminate their impact. I've seen many people decide one day to "play around with the monitor", and they may turn on one or more of these start buttons. They may even yawn if they don't find things compelling (though there's really SO much to appreciate--see my articles on the monitor). My point though is that if they close the monitor, they may think "so much for the monitor". Au contraire, mon frere.
The work done by the start buttons (monitoring, profiling, or memory tracking) is done by CF, the server instance itself. The monitor is just an interface to view the info that it is gathering. So if you have no intent of ever looking at the monitor, then DON'T leave those buttons.
On the other hand, I'm not saying "don't leave them on". You absolutely can and SHOULD leave them on, and yes, even in production, if you find them valuable and find that they have no impact, or acceptable impact.
You can turn them off, even without getting into the Monitor
Finally, what if you have turned them on (let's say "memory tracking"), and you're in the situation where it's now killing your server. If you can't even get into the monitor to turn them off, you're going to be in quite a pickle, and understandably panicked.
Fortunately, you can turn the buttons off without getting into the monitor. It's easier on CF 9.01 and above, but you can also do it by manually editing a file in CF 8 or 9.0. I'll address that in another entry.