A sound tech posed the question "what you think of guitarists putting reverb and delay on, rather than us doing the processing?"
I don't have a problem when a guitarist uses reverb or delay for a particular service or song as long as it sounds good. That being said, there are several factors to consider;
1. Does the guitarist have any idea what they are doing? They might think an effect with tons of reverb sounds really cool (and it might) but it might not work for the song in which they are playing. They might not have any idea what they are doing (i call this young and in love) and therefore think "more reverb or delay equals better tone."
2. Does the guitarist have access to the house mix so they can hear how their tone sounds in the overall mix? You can't keep adding pepper unless you occasionally taste the chili.
3. Does the guitarist have a better ear for reverb and delay than the sound tech?
I like taking as much control over sound as possible. I also know there are times when it's better for the guitarist to take control over certain aspects of their sound. One guy runs his acoustic through a POD XT Live. He sends a signal with a better tone than if we just pulled from his guitar. However, as far as reverb / delay, he doesn't add anything. Therefore, the sound tech adds in what is necessary. When I play acoustic, I run through an effects box (lr baggs di) that gives me the perfect tone that doesn't need reverb added – really, it's that sweeeeeet.
I don't think there is a simple answer of "the guitarist should control reverb/delay" or "the sound tech should control reverb / delay." Much of it comes down to the need to add it, and the way in which it's used. For example, I've had times when I've asked a guitarist to turn down their reverb and then I added some back in the mix. The reason was they were sending too much. I don't know if it's because they didn't hear it in the house mix, they didn't dial it in for that particular song, or they thought it was perfect when they practiced it alone.
Asking kindly "can you turn down the reverb or [insert other effect]?" is usually successfully. If you are dealing with a tone-junky, then you might have a much harder time. "It sounds perfect with this song; I worked on it alone last night for an hour." So they worked on their tone – but it was not with the rest of the band and it was at home so it's not going to have the same sound as in the house mix.
Having talked with tone-junkies, the best thing you can do is meet them some time and ask about tone and guitar effects. Let them educate you in how guitar effects work from their point of view. Then, after you have established a respectful relationship, you can teach them a bit about the different factors that contribute to mixing a guitar in a song. At that point, as long as they are equally respectful, you are now on more equal footing in their mind to make suggestions. The next thing you know, THEY are asking YOU "how does my distortion/crunch/fuzz/reverb/whatever sound in the mix?"
If you are lucky, you've got guitarists who know exactly how to dial in a particular amount of reverb or delay and adjust it on their effects pedals for each song. This makes your job easier. Even if you are blessed with this situation, I still suggest you ask them to teach you about their effects and tone controls. The more we learn from each other, the more we respect each other and the easier it is to work towards a common goal.