Too easy for a scammer to just keep the money and not show up.  I have never done deposits.

I can understand for an "overnighter" or a 24 hour appointment to pay  25%+  upfront.  But that amount is more than I would ever want to carry in cash anyways

I've been burned twice.

 
It's up to you to decide if the reward merits the risk.

Not worth the risk. IMO. If they’re requested I don’t bother. Some providers might not like reading this and I get why, especially the legitimate ones, do ask for this. But 90% of those asking for advances are scammers and you’re opening yourself up to a disaster. I just went through hell dealing with a SB so because of that, this is where I draw my personal line.

..... the companion is well-known and reputable.  I have sent many deposits to such companions, and have never had a problem.  Guys, we have to understand their realities, and their need to secure a commitment rather than reserve a time, and turn away other business, for someone who may just not show up.  It happens to them ALL THE TIME.

There are times when a companion is not well known that I'll hesitate, but those with a long track record of reviews and an active Twitter profile are just not a problem, in my experience.

I would no more do that than I would ask a provider to let me pay her a week after the appointment.

If the provider is well known then yes, otherwise forget it. Sila Star requires a deposit but she has pages of reviews.  She's not going to screw up her reputation.