In response Sadiq Khan has told each of them to "direct your anger" at the transport app and not TfL.
But should you be angry? And should you sign in the name of cheaper fares?
The petition - which was set up by Uber itself - has raised eyebrows amongst some who question why people are lobbying for the reinstatement of the Uber's licence rather than for the company to raise its standards.
In its announcement of the decision, TfL outlined four reasons Uber "is not fit and proper to hold a private hire operator licence".
HuffPost UK asked TfL to elaborate but was declined as the legal case is still ongoing but there is already relevant information in the public domain.
Here's a roundup.
1) Its approach to reporting serious criminal offences.
The Met Police said last month Uber was failing to report sex attacks by drivers in order to protect its reputation.
Insp Neil Billany outlined how lack of action by Uber resulted in delays in prosecutions during which time perpetrators in some cases committed further criminal acts.
2) Its approach to how medical certificates are obtained.
All Uber drivers are required to undergo a medical showing they are fit to drive.
An investigation by The Sun last year found some GPs were selling faked "all clear" forms for cash, "simply making up the results of blood pressure and eyesight tests".
There was no indication Uber in any way promoted the practise.
3) Its approach to how Enhanced Disclosure and Barring Service (DBS) checks are obtained.
The (DBS) is a government agency that checks criminal records for, amongst other things, unsuitability to work with children or police warnings.
Earlier this month TfL told Uber all its drivers would have to undergo new DBS checks with a specific provider.
Other third-party providers were allowed but TfL after a "recent review of policy" decided it would not use them anymore.
TfL did not elaborate on the decision.
4) Its approach to explaining the use of Greyball in London
Greyball is a piece of technology that allows Uber to show different users different versions of the app.
It was allegedly used in cities worldwide to evade regulators by alerting drivers to city officials hailing a ride so they could avoid picking them up.
The official would then be shown a different version of the app populated by fake Uber cars.
The head of Uber's European operations, Pierre-Dimitri Gore-Coty, has denied the company used Greyball in London.
Sadiq Khan's latest statement (Saturday):
Transport for London (TfL) yesterday informed Uber London Limited (Uber) that it will not be issued with a private hire operator licence after expiry of its current licence on 30 September. This decision was made independently by TfL as the legal taxi and private hire regulator for London.
TfL has concluded that Uber's conduct is not fit and proper to hold a private hire operator license. TfL considers that Uber's approach and conduct demonstrates a lack of corporate responsibility in relation to a number of issues that have potential public safety and security implications. These include Uber's approach to reporting serious criminal offences, its approach to how medical certificates are obtained and its approach to how Enhanced Disclosure and Barring Service (DBS) checks are obtained. Read more here: http://bit.ly/2yhssmC
I have written for The Guardian about why I have backed TfL's decision -
read more here: http://bit.ly/2hoqQ3B - however, I want to be absolutely clear that there is a place in London for all private hire companies that play by the rules.
Uber's current license does not expire until the end of September so the service will continue until then. The company can also continue to operate until the appeals process has been exhausted.
I know that Uber has become a popular service for many Londoners – but it would be wrong for TfL to licence Uber if there was any way this could pose a threat to Londoners' safety or security.
As Mayor of London I welcome innovative new companies that help Londoners by providing a better and more affordable service – but providing an innovative service is not an excuse for not following the rules. All companies in London must play by the rules and adhere to the high standards we expect - particularly when it comes to the safety of customers.
I have every sympathy with Uber drivers and customers affected by this decision but their anger really should be directed at Uber. They have let down their drivers and customers by failing, in the view of TfL, to act as a fit and proper operator.
I suspect it will take some time before this situation with Uber fully plays out. In the meantime, I will continue my work to help support innovative businesses in London and to create a vibrant and safe taxi and private hire market.
Mayor of London