Yes you, mage, I'm talking to you.
If someone asks politely for a portal and you don't want to, a simple "No" will suffice.
When I play alts and I need a portal, I am always respectful and generally offer more than the going rate for a portal. The one thing that gets me just furious is when you get ignored completely. Look dude, I know you aren't AFK, I see you jumping around on top of the mailbox. Just reply please.
If someone asks me in a polite manner, I always give a portal, if they ask in a less than polite manner but offer gold, I will do it. If they are complete idiots or rude, I tell them so and refuse to do it.
A 3 second reply works wonders guys, stop being a bunch of pricks, I'm nice about constant portal spam, it's part of the class, you can be too.