NEW YORK ( TheStreet) --There is way too much enthusiasm and money aimed at capturing a slice of the mobile payments market, and yet it could be awhile before savvy investors find a way to pop this bubble. The latest sign of the euphoria came with investors' response to a partnership between Discover Financial Services ( DFS) and eBAY ( EBAY) PayPal, which will enable PayPal account holders to make payments at stores that accept Discover cards. eBay shares gained 2.51% following the deal's announcement Wednesday, while Discover shares were 3.86% higher on the day. The partnership comes fast on the heels of a similar deal between Starbucks ( SBUX) and Square two weeks ago. But shorting eBay is still too risky. It trades at a reasonable 16.5 times earnings--only slightly above the 14.5 multiple of the S&P 500. Besides, PayPal is potentially getting access to 7 million new customers as part of the deal, according to Bloomberg. Potentially is the key word there, but that potential may be worth a 2.5% increase in eBay's valuation. Discover is a more tempting short, but the credit card lender's shares haven't risen 170% per the past two years on optimism over mobile payments. Instead, it's the much less sexy but far more powerful ongoing shift of more and more transactions around the globe from cash to plastic and electronic. Besides, it trades at just eight times earnings. Surely if Square were publicly traded, it would make a nice short candidate. The company was seeking a $3.25 billion valuation in late July--and that was ahead of the Starbucks announcement. According to The New York Times, that's 13.5 times Square's valuation of just two years ago. In a sign of how frothy things have become, research firm Candlestick Advisors estimate Square's valuation at between $1.29 billion and $1.43 billion in a July 11 report--well below the numbers cited by the Times. And what about Starbucks? Its shares are up more than 10% since it announced its deal with Square. But its not clear how much of that can be attributed to the deal with Square. Caribou Coffee ( CBOU) shares are up more than 13% over the same time period.