Phil makes a good point about making an informed decision about how much risk your group is willing to accept. What works today (taking a risk because people are trustworthy) might not be appropriate down the road when newcomers are in charge. At that time, it may be too late or too awkward to institute a tighter financial control.
Our treasurer can turn around a reimbursement check within two days, faster if she knows it's urgent. But...all three authorized signers in our PTO live within 2 miles of the school and are available during the day. Easier than some situations, but so important to us that we won't bend the 2-signer rule no matter where our officers live. Also, if your PTO wants bonding insurance (a very good idea and another form of financial control), you are required to have a 2-signature policy.
Sterling - financial controls are not designed to make the treasurer's life easier, just less risky. Two signatures is a must in my book. It's not just about whose name is on the actual check, but also who has authorized and signed off on the paperwork that accompanies the check.
Coming from a PTO that dealt with embezzlement a few years back, we are required to have two signatures on every check and the person the check is made out to cannot be one of the signers. We also have co-treasurers.
If your group does not already have a Charter or by-laws, you can decide what financial checks and balances will work for you. However, what Critter described are basic policies and procedures your should adopt and adapt to your needs.
For our group, only 3 of the 4 Exec Bd members have authority to withdraw money from the account (or write a check). They are the Treasurer and the 2 Co-Presidents.
However, we have always gone with a one signer policy and we have decided to continue doing this. To minimize the risk we require the paperwork Critter suggested (invoice, bill, or a reimbursement form with receipts attached) before a check is written. The books are supposed to be reviewed by a person independent of the board at least once a year. And none of the authorized signers are allowed to sign a check to themselves, ever.
I don't think "difficult" is a valid reason to having a single signer on a check, but for your group there may be other valid reasons. For us, people are used to paying out for authorized PTO expenses out of their own pocket and getting reimbursed. Often they want to be reimbursed quickly and it is more convenient for the membership if there is one signer rather than needing two. But we understand the risk we are running and we believe the risk is low and worth the benefit of a single signer. There is a certain amount of trust involved in this for us -but then if there is a question of trusting your Treas. or Co-Pres. then you have issues already.
(I am not saying this is the way your group should go - Critters is a lower risk approach - I am just say this is a way your group could go.)
We also require 2 signatures. The treasurer, president, principal and school secretary are all signers on the acct. We added the principal and school sec. because sometimes its easier to get their signature since they're at school. The treasurer always signs then one of us.