Would make me think it's the day tickets went on sale back in Feb/March.

...on the grassy knoll.

Go south on N Clark all the way next to the Sports World store and look back at Wrigley. You'll notice that the crowds from the previous photos in front of the ball park disappeared.

Nice way to tour the area, though. Out of curiosity, did Google use the funny-looking Google Truck in Chicago like they did in San Francisco? The truck was so recognizable that people stopped on purpose to get photographed on the streets of SF.

Top of Soriano billboard is visible over the YumYum building.  Railing buy Admin office door was new this year.  Plus blue & white cap design on a girl in the crowd is from this year.  And 2007 is on door of SportsWorld souvenir store.

Looks to be after a game, based on late afternoon shadows and the long line of fans waiting to board Pace bus on Clark.  Also fair to say it's a montage of photos - several 'seams' are evident where people are merging into other people or just an arm or leg appears.  Either that or it's an X-files episode...

Per earlier post by kidk about marquee message, the women's 3m diving event at World University Games was Aug 18, so this would have to be after that.  Interestingly enough, the marquee message I see is something about earning extra bases points, whatever those are.  Red hats seem to be second most popular color amongst the crowd, but it doesn't look like Cardinal red.  More like that Houston or Arizona stupid softball league red.

Looking at schedule shows Houston in town Aug 31 weekend.  Sunday was the warmest of the three days (High of 84F) so my guess would be Sunday, September 2.  The clincher is if you zoom in on the players parking lot, you can see Eric Patterson getting out of a cab, late again...    ;-)

Finally, yes, I think Google used their funny looking truck.  If you look east on Addison then pan down, you'll see the shadow of the vehicle taking the pictures.  It appears to be an SUV of sorts with a big 'bubble' on the roof.  I imagine that's where the camera is housed.

Ok, I have way too much time on my hands....

They drive thru the area a few times with the truck/car with camera on top, and then pick the best shots for an intersection/area.  Much like the best take on a scene in the film.

That's why if you go further north on Clark that the fans disappear, because they used a separate set of photos it's not not close to game time and they used another set of photos.  Major changes like that happen at intersections usually where they used another vehicle's data or a different time when the car went thru the other way.

That's also why you can move thru the intersection and see the same car or person move from one point to another.  

They don't really have the time to composite fake people in front of Wrigley and to have them appear to be moving.  I have seen examples of people finding themselves on Street view leaving/going to work and the similar.  

The July-August timeframe seems right, that was the period of time people were spotting the vehicles around Chicagoland.