Is this a sensible way to implement a model?

Is this a sensible way to implement a model?

I've created the following model for an academic project, and I'm wondering if this is a sensible way to manage a model:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using System.Runtime.Serialization;
using System.Collections.ObjectModel;
using System.Windows.Forms;

namespace IceCreamShop
{
    [Serializable]
    public class Customer : ISerializable
    {
        private const string SAVE_FILE_NAME = @".\Customers.bin";

        #region static model accessors

        private static List<Customer> customers = new List<Customer>();

        public static ReadOnlyCollection<Customer> Customers
        {
            get
            {
                return customers.AsReadOnly();
            }
        }

        public static int Cardinality { get; private set; }

        public static void saveCustomers(List<Customer> customers)
        {
            IFormatter formatter = new BinaryFormatter();

            Stream stream = File.Open(SAVE_FILE_NAME, FileMode.Create);

            formatter.Serialize(stream, customers);

            formatter.Serialize(stream, Customer.Cardinality);

            stream.Close();
        }

        public static void loadAllCustomers()
        {
            IFormatter formatter = new BinaryFormatter();

            List<Customer> customers = new List<Customer>();

            try
            {
                Stream stream = File.Open(SAVE_FILE_NAME, FileMode.OpenOrCreate);

                if (stream.Length > 0)
                {
                    customers = (List<Customer>)formatter.Deserialize(stream);

                    Customer.Cardinality = (int)formatter.Deserialize(stream);
                }

                stream.Close();
            }
            // Shouldn't happen during normal operation, pending any permissions/file write issues
            catch (Exception ex)
            {
                throw ex;
            }

            if(customers.Count == 0)
            {
                // Dummy customer for patrons who don't want their data tracked
                customers.Add(new Customer("nobody", "nobody"));

                Customer.Cardinality = 1;
            }

            Customer.customers = customers;
        }
        #endregion

        #region individual model data

        private string firstName;
        public string FirstName { get { return firstName; } }

        private string lastName;
        public string LastName { get { return lastName; } }

        private int id;
        public int ID { get { return id; } }

        //Used externally to generate a new customer
        public Customer(string firstName, string lastName)
        {
            this.id = Customer.Cardinality++;
            this.firstName = firstName;
            this.lastName = lastName;
        }

        #endregion

        #region serialization

        Customer(SerializationInfo info, StreamingContext context)
        {
            this.id = info.GetInt32("i");
            this.firstName = info.GetString("j");
            this.lastName = info.GetString("k");