Only because it turns some experienced buyers off. And your dream buyer is an experienced buyer.

A reserve means the seller can bail at any point up until that reserve is met.

Imagine that you're selling a laptop that's going for around $800 in other auctions. But you're not entirely sure you even want to sell your laptop. You put a $2,000 reserve on it just to leave the option to bail available at the end. An experienced buyer realizes this and will likely just pass on your item out of principle.

If it would make you feel better to place a reserve on your item, at least state right up front what your reserve price is and why you've placed it in the first place.

In my experience, however, I've never once been low-balled on an auction. There's a median price for your item in it's condition across the entire marketplace. If you're OK with that median price, don't post a reserve.

Spell your brand and product name correctly and you're virtually guaranteed to get close to that price in the end.

I've benefited before from eBay flukes so I always set a reasonable reserve price. I wouldn't suggest setting it too high but I think people understand there is a minimum price you're willing to sell at. I also usually set a buy it now price, requiring immediate payment, at about a 5-10% discount of other recently completed auctions for the same item. If someone is willing to save me the hassle of answering tons of questions, or re-listing the item when inevitably the first few buyers don't pay, I'm happy to give them a discount. In my experience with eBay in the last few years don't be surprised at all if you have to list the item several times before you find a paying buyer.