By Alexandria Sage

SAN FRANCISCO (Reuters) - EBay Inc (EBAY.O: Quote, Profile, Research) on Wednesday provided a cautious near-term outlook that reflected concern over a weak U.S. economy and changes it has been making to its auction business, sending its shares down 7 percent.

Investors have come to count on eBay raising its outlook each quarter, and were disappointed when the company said that revenue in the current quarter would be lower than expected, while leaving its full-year projections relatively unchanged.

That overshadowed a 22 percent gain in second-quarter net profit that beat Wall Street estimates, helped by a surge in listings and share buybacks.

"It's ancient history now, but in past years, investors knew eBay would start out each year conservatively and raise their outlook more and more as each quarter went by," Global Crown Capital analyst Martin Pyykkonen said.

"What eBay is saying now is, 'We don't want to go out on a limb,'" Pyykkonen said. "The economy is working against them."

Moreover, Bernstein Research analyst Jeffrey Lindsay said investors may have oversized expectations about how online sellers can perform in the weak economy.

Average selling prices for eBay fell in the second quarter due in part to more shoppers in the United States and Britain shifting to lower-priced goods, executives said.

The company has been lowering upfront listing fees to attract more sellers in response to slower growth in its main auction business over the past three years.