Currently, the installer does not check if the given credentials have enough permissions for piwik to run normally.

Example
I gave the MySQL permissions:

Select_priv,Insert_priv,Update_priv,Delete_priv,Create_priv,Drop_priv,Index_priv.

"Alter_priv" was missing and is quite critical for piwik to run. At the first start (or at the end of the installer) it tries to alter a table.

The quite easy and automatic webinstaller feels good and gives an impression as if everything works fine when you see those green check marks. But in the end, it failed horribly. It didn't put any error message or whatsoever in any logfile or log facility that I know of although the column "location_provider" in table "piwik_log_visit" was missing!

Please check for those db permissions right after db credentials are given. And ... if permissions are missing, please log an error somewhere!

Cost me three hours to find out about that. :( me sad.