There are a growing number of apps designed to help people find parking, and even reserve and pay for parking in advance. Some know the state of lots. These apps are good for the user but also can produce a public good by reducing the number of people circling looking for parking. Studies suggest in certain circumstances a large fraction of the cars on the road are doing that.
This weekend, I attended the Maker Faire. I've been to almost every Make Faire, including the first, and now it's grown to be far too successful -- you can hardly walk down the aisles at the busy times. They need more space and a way to put more of it outside so thin out the crowds. Still, it is one of those places that makes you feel very clearly you are in the 21st century.
Early on Maker Faire realized it had a parking problem. The lot at the fairgrounds fills up now even before the event opens, and they manage various satellite lots and run shuttle buses to them.
This year they tried something interesting, a twitter feed with parking updates. They tweeted when lots filled up or re-opened, and suggested where to go. They took some limited feedback about lack of shuttles. I think that it by and large worked and reduced traffic around the event.
However, my judgment is that they were not entirely honest in their tweets. This year, and in prior years, they strongly encouraged people to go to one of the most remote lots, regularly telling people it was the fastest route to the event. This was not true. I don't want to ascribe any particular malice here, but there is a suspicion that there is a temptation to make reports in the interest of the event rather than the user. This does have positives, in that cars diverted from near the event reduce traffic which makes the shuttle buses run much faster, but if you give wrong information (deliberately or by accident) this means people stop trusting it and you get the traffic back as more people ignore it.
For example, we stopped at a remote lot, and saw a very long shuttle line. We drove on to a closer lot (also reported as having spaces, but not reported as clearly a better choice) to find lots of spaces, no shuttle line, frequent shuttles and also a walk that was only slightly longer than the shuttle trip.