Verbal is exactly what it means, people change their minds especially when it comes to money.
If the seller(s) are good and honest people they will not entertain another offer or allow anymore showings of the home during the due diligence period. If the seller(s) agent feels in their professional opinion that the deal is shaky he or she may discuss that with the seller(s) and suggest that they continue to show the property. The inspection(s) are a buyer expense which the buyers know are not refundable. As Javier mentioned in a previous posting and Gale only a fully executed contract is a true binding agreement. Always get things in writing 1st and then being your due diligence period.
A good agent will advise you accordingly.
Feel free to ask any questions about your experiences we are here to help.