Hi,
For HikaShop, we want to make an integration with the Joomla 3 tag system. The problem is that the tag system is not completely API "stable" (it is working great but the API is still changing, so there are differences between Joomla versions).
So we can't implement yet the Joomla 3 tag system.
So, the idea fpr the moment is to use a product custom field.
In HikaMarket 1.3.0 (that we are currently finishing) you will have to possibility to create custom fields and to assign them special display rules.
So a custom field can be display in the front-end (to the customer) but not editable by a vendor. In the other hand, a custom field can be editable by the vendor and not display in the front-end product page.
The last sample allow you to have a value that can be use by a "tag cloud system" (as a hidden data).
The custom field could contains the list of your tags and the "tag cloud system" could read the product values in the database, in order to make his display.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.