These petitions are worthless because it's an appeal to the federal government. If they truly want to secede, they'd send something like this to the state legislature. At that point, their respective Congresses will either give the yay or nay to secession, at which point they will request their departure from the Feds.
Economically, it's a disaster for the states. You have to understand, the economy in this age is globalized - every country has a penny somewhere on this globe other than their own home ground - and most countries have pennies everywhere. These new states won't. And they'll have no credit record or anything, which doesn't look good for a company wanting to invest in a new country. Likely, companies will leave for states that haven't seceded where the United States is still in control, and therefore a safe bet. All these companies leaving will slam the state's economy and ultimately cripple it, if I understand correctly.
Also, the federal government isn't just going to let a state secede just like that. The United States is going to make sure all of its federal offices and aid are out of there. Yes, this means the Post Office will permanently close. The National Weather Service offices will close. The military bases? Military is federally controlled, so they will likely pull them out. Oh, and FEMA. Good heavens, states like Louisiana and Texas (who already got past the 25,000 signatures) will be in a load of trouble the next time a hurricane hits them hard - there's no federal government to assist them rebuild.
So now you're losing companies making you money, you're losing federal aid, and you're losing any defense you originally had as part of the Union. Long story short, it's not a pretty picture.