Someone on this board has four ten-night reservations in DC in July -- only a few weeks away, and has had three of them for at least two weeks while getting input on this web site. Other people on this board are scrounging for rooms in DC in July.
If a lot of people tie up hotel rooms with multiple bookings, hotels will have to overbook even more than they already do, tighten their reservations policies, or charge a small nonrefundable reservation fee.
How many multiple bookings are OK?

How many people have CANCELLED the ONE booking they had because of gas prices?

Anyone "scrounging for bookings" didn't plan far enough in advance IMO.

Honestly, I doubt anyone is scrounging for hotel rooms in DC in July. It is so ungodly humid in July, not exactly peak tourist season.

IIRC, the poster with multiple bookings has a much more generous budget than those who are "scrounging."

If this were a genuine problem, hotels would not allow penalty-free cancellations as few as 24 hours in advance. But they do. Which leads me to believe it isn't a genuine problem.

Because multiple bookings are becoming a problem, some hotels have begun requiring cancellations further than 24 hours in advance.
The most common solution for hotels is to overbook the rooms (like airlines do with seats). That's why it's possible to have a guaranteed reservation and arrive at a hotel and discover it has no room for you.

I have been subject to overbooked hotels on business trips to Washington. I was coming late from Dulles, and my room was gone. They sent me by cab to a comparable hotel, and everything was fine. I might have felt different if I were with my family, but it wouldn't have made any difference. They can't conjure rooms out of nothing.

Blocking multiple reservations is bad manners, like sneaking food from the hotel buffet to eat for other meals. Oink, oink.

For what possible reason (other than too lazy to complete research) would someone possibly want to exert (albeit minimal) effort to make multiple hotel reservations?

The other side of the "Too lazy to do research" coin is "Too compulsive to finalize the research". Trying to make the absolutely BEST choice, rather than one that's merely good enough, is an exhausting process.

<<to make the absolutely BEST choice>>

We're talking about a 10-day hotel stay, right, not a bride or a surgeon. I would think the second best hotel would be perfectly acceptable (as would the third or fourth!).

They can't conjure rooms out of nothing.

Well, maybe. We showed up at 10 p.m. at a Marriott at Disneyland. Our kids were probably 3 and 5 at the time. They told us they were overbooked and they were going to put us in some other Marriott 11 miles away. We promptly propped my 3-year old on the counter, and said firmly, "We booked a hotel across the street from Disneyland because we want to BE across the street from Disneyland....If the president showed up, would you have a room for him; well, he's not coming!. We not only got our room for that night, we also got a free weekend stay, and when we did take advantage of that free weekend, our room had a tray of cookies, milk and fruit in it when we arrived!

"We're talking about a 10-day hotel stay, right, not a bride or a surgeon. I would think the second best hotel would be perfectly acceptable (as would the third or fourth!)."

Oh, I agree 100%! But some people make ALL their decisions as if they were choosing a bride or a surgeon; the notion of "good enough" just doesn't occur to them. As I said, "too compulsive." Even if they have found 3 or 4 hotels that meet all their choice criteria, they then start looking for ways that one is different from the others.

My sister does this; she would end up asking for opinions on which hotel had the softest carpet or the best muffins at breakfast, or something. When she and I travel together, I do the planning and she does the driving, otherwise we'd both be frazzled and exhausted.

I am compulsive about trying to find the best hotel (in my price range), so I look at as many sources as possible and try to figure out which ones are most reliable and consistent with my taste. However, I still find it very inconsiderate to book four hotels at the same time for a stay during the peak summer vacation period. I wouldn't do it.
Wouldn't it be ironic if the hotel that the person finally picks is overbooked when he arrives.

While I don't see the advantage to booking 4 hotels, I do book the best priced (cancellable) reservation I can find at the time of original trip planning. Many times a last minute deal will come up that is much more cost effective. I will then cancel the first and book the second. This strategy saved me $100+tax per night in NY recently. Its not always "too lazy to do the research" that causes the change, but the policy of hotels trying to fill rooms at a late date and offering deals not available earlier. How many book a back up room when trying to use PriceLine?

TC, many of us will try Priceline after booking a cancellable reservation. But not 4 of them.

Our group of 4 now has 3 res. in NYC, the most recent was made because of a 1/2 price rate special(all are 3-4 star, $300/night & up). Yes, two will be cancelled, probably more than 2 weeks prior to visit, but it can pay to keep looking for a better buy. We will chose the one that fits our budget, location and needs.

But the question is, since you already found a "better deal", why not cancel the other two? You can still wait for an even better deal without hogging all the available reservations.

My point exactly. There is no good reason to keep so many reservations for so long.

My answer to your original question is none! If absolutely necessary for a day or so, b/c of uncertainty about dates or prices, I might waiver a bit. Otherwise, I think it is entitled---not to mention unethical--- behavior, IMO.

Holding multiple reservations isn't very respectful of the businesses. If you aren't going to stay at a place you should let the hotel re-sell those rooms to real guests.