Stock-based compensation expense. This expense consists of expenses for stock options, restricted stock and employee stock purchases. eBay excludes stock-based compensation expenses from its non-GAAP measures primarily because they are non-cash expenses that management does not believe are reflective of ongoing operating results. eBay also excludes its proportionate share of Skype's stock-based compensation expense.Employer payroll taxes on stock-based compensation. This amount is dependent on eBay's stock price and the timing and size of exercises by employees of their stock options and the vesting of their restricted stock, over which management has limited to no control, and as such management does not believe it correlates to eBay's operation of the business. Amortization or impairment of acquired intangible assets, impairment of goodwill and significant gains or losses and transaction expenses from the acquisition or disposal of a business. eBay incurs amortization or impairment of acquired intangible assets and goodwill in connection with acquisitions and may incur significant gains or losses from the acquisition or disposal of a business and therefore excludes these amounts from its non-GAAP measures. eBay also excludes its proportionate share of Skype's amortization of acquired intangibles expense. eBay also settled a legal exposure in conjunction with the acquisition of a business and excludes this settlement payment. In addition, eBay's results are also impacted by hedge transactions related to unique movements of cash from significant business acquisitions or dispositions. eBay excludes the impact of the accretion of a note receivable associated with the disposal of certain businesses. eBay excludes these items because management does not believe they correlate to the ongoing operating results of eBay's business. Restructuring. These charges consist of expenses for employee severance and other exit and disposal costs. eBay excludes restructuring charges primarily because management does not believe they are reflective of ongoing operating results. Income taxes associated with certain non-GAAP entries. This amount is used to present stock-based compensation and the other amounts described above on an after-tax basis consistent with the presentation of non-GAAP net income. In addition to the non-GAAP measures discussed above, eBay also uses free cash flow. Free cash flow represents operating cash flows less net purchases of property and equipment. eBay considers free cash flow to be a liquidity measure that provides useful information to management and investors about the amount of cash generated by the business after the purchases of property, buildings, and equipment, which can then be used to, among other things, invest in eBay's business, make strategic acquisitions, and repurchase stock. A limitation of the utility of free cash flow as a measure of financial performance is that it does not represent the total increase or decrease in the company's cash balance for the period.