Cosmopolitan View

Although I in general agree with your “lesson learned”, in the case of Cosmo and its views another key lesson is that it is important to do some basic due diligence about views or anything else that matters to you.
At the time of the Cosmo presale, plans were already in the works for a 13-story office building immediately across the alley from the Cosmo site. The proposed building was based on application number #2401880, found on the DPD website. Early design guidance meetings dated back to 5/18/2004. Master Use Permit decision was made on 8/25/2005, based on the plans on file as of 8/3/2005, with appeals due by 9/8/2005. This was for a building that was to fill much of the space on the property across the alley from Cosmo, backing up to the alley where there would be a 2-foot cantilever above 16-feet. Plans called for ground level retail, office floors above that, parking for 235 cars below ground, and additional height for a screen wall to hide the rooftop mechanical systems.
How tall? The documentation I’ve seen say less than 300 feet, which was the maximum permitted at that location at that time for an office tower (a limit also reported in a Seattle P-I article). “less than 300 feet” of course isn’t very specific). Because new offices tend to have higher ceilings and drop ceilings, a 13-story office building might reach up to the 18th-25th floor of a parking+residence building, based on other nearby buildings at the time of the pre-sale and whether Cosmo itself has a 13th floor (e.g., the 20-story courthouse is taller than 32-story Metropolitan Tower Apartments).
(In addition to the view question, you might not want the noise of a roof-top mechanical system that close to your own windows.)
There was a lot of fuss in various blogs some time after the pre-sale in the months near Cosmo closings about how the city changed the zoning on the property across the alley to allow a high-rise with no tower spacing. That was misleading, to say the least, as they routinely neglected to mention the building plans that were already underway when they signed their pre-sale agreements.
Again, at the time of the pre-sale, no spacing was required across the alley. When the city was in the process of revising its master plan, there was a proposed change to tower spacing in the neighborhood, but that proposal grandfathered in the existing plans. The proposed tower spacing rule ultimately was not enacted for that location so there was no spacing change, but a higher building was allowed, after which the developer then pursued the higher building. A 60-foot tower spacing rule would have made the extra height impractical for the property across the alley, so had the tower spacing changed, the developer would likely have stuck with their original grandfathered plans.
So at best your “lesson learned” applies primarily to the folks living in west-facing Cosmo units on the upper floors, as they were affected by changes in plans across the alley. Below that, however, prospective Cosmo buyers either looked into the plans for across the alley and decided to live with them, or they didn’t bother with basic due diligence about the views.
And given how many tower and non-tower apartments and condos there are downtown and up on Capitol Hill (and probably elsewhere in town) that face other buildings across the span of an alley, and it’s not unreasonable to think that some Cosmo buyers just aren’t bothered by their new neighbor.

The Seattle Department of Planning & Development website lets you search by address or project code.
If Wendy allows websites in answers, I’ve copied a link to the specific search page here:
http : //web1.seattle.gov/DPD/permitstatus/
Search for project 2401880.
Searches in the search box in the upper right corner for the project number connect you to some of the early notices. They report that the site at the time was zoned “DOC2-300” – “Downtown Office Core 2 with a 300’ height limit”. The notices also show the usual overhead view drawing of the property with the proposed building sketched in – it backs up to the alley.
As an FYI, once the height restriction was dropped, the developer changed plans to a taller building – look for #3004017 for details on that project.
The site could be better organized, but you can search by address or project number.
As for air easements, I haven’t come across anything there – the only examples I’ve heard of were negotiated between property owners.
But the DPD site also has a lot of information on zoning. There may be relevant info there.

Here’s a news bit from The Stranger that should make some of the Cosmo owners smile.

If it’s any comfort to the Cosmo-west owners, they may have to stare into the building next door, but they’ll still have privacy – since there are NO tenants for the office tower looming over them.