Phil,
I have three different cards that if maxed, would equal 50% of my average annual salary (each card has roughly the same limit), so yes its possible.
One of the cards is a no-fee rewards card, its the only card we use. My wife and I buy almost everything on it, and pay it off EVERY month. Its great because we pay no interest on the charges, gain rewards points, and our cash account has more money for longer periods to earn interest between billing cycles. Word of warning though, it takes me, and especially my wife, a good deal of discipline to stick to that plan. Quicken's reminders are a life saver though!
I can't remember that last time I used the other two cards. I guess if I ever run into a ransom situation in a foreign country or something, they might come in handy!
To answer your original question, In my younger days, when one of my cards was lagging behind the others, I would call and tell them I was considering cancelling. They would usually run a quick credit check and up my limit to compete with the other cards. Most of my credit increases came without warning or request, though. By either neglecting a card for a while, or using and regularly paying off a card, they just kept upping limits. They have never verifed or even asked my income unless I initiated the increase.
I doub't that a newly issued card will give out the kind of limit your looking for, nor do I suspect and existing card will allow you to jump from 10% to 40% at once (especially if YOU initate the increase). Your best bet is to talk with the card company. If your salary has doubled since they issued the card, a credit limit increase of 100% would not change the debt to income ratio they thought they were giving you.
Good Luck and be smart!
P.S. my Dad's Lowe's card has almost a $100k limit. It started at $5k and he has never once asked for a credit increase. He loves Lowe's though.