TL;DR: Get rid of all of them. Even Apple.
I think there might be questions for which these vendor tags might be useful
- about the integration of different technologies by the same vendor, like e.g. iTunes/iPod/iOS/Mac OS X (combined e.g. with sync?) for Apple; that would exhaust the tag count limit too easily. The same with very few other vendors, such as Microsoft (anyone else?)
- It also helps to refer to more obscure products in combination with other tags, as for example, here or here. Since the site supports looking up topics with specific tag combinations, this could prove useful for vendors that don't warrant their own product tags, like apple&laptop instead of macbook
- If you're looking for a solution to a problem of yours from a specific vendor (vmware comes to mind). But why ask here instead of calling their sales hotline?
But, checking the more popular questions in the apple tag, I can't help but notice that almost all of them would work just as fine without these tags — osx or mac gets 90% of these topics, and apple doesn't add anything for these.
Vendor tags just doesn't provide enough information on its own. I can actually see that a question is about the Apple Cinema Display without using apple; display is enough here.
Ultimately, one has to ask whether tagging questions with a vendor name helps in organizing questions. For example, if I were to be interested in either learning about or helping others with vim, I could check out vim.
But a tag for some vendor? Let's face it, just because I own an HP laptop doesn't mean I want to read or answer questions about LaserJets. Companies rarely make a single product or line of products, and if they do, there's a tag for the product already.
Even apple, which is somewhat useful according to @JeffAtwood, probably because the most popular products are rather closely related, encompasses
- Desktop and mobile computer hardware mac, macbook, and others
- A desktop and server operating system osx, osx-snow-leopard, and others
- A family of portable MP3 players ipod *
- A mobile phone iphone, iphone-4, iphone4 *
- A mobile operating system ios *
- Network hardware time-capsule, airport-extreme, airport-express, airtunes
- Peripherals (mice, keyboards, screens) magic-mouse, mighty-mouse, and possibly others
- A tablet computer ipad *
- Server hardware (discontinued, but not too long ago) xserve *
- Consumer/desktop software ilife, itunes, iphoto, garageband, and others
- Office software iwork, iwork-09, pages (not all of these), iwork-numbers, keynote
- Professional video/audio editing software
- A web browser and its underlying engine safari, webkit
- An online-store for music, movies and TV shows, e-books, itunes-store
- and software app-store
- an online service (soon two, actually), for storing data and syncing and stuff *
- A totally failed "social network for music" (Ping) *
- Some SAN storage thingy I have never heard anyone using *
- There's also an IDE (xcode), GUI builder, programming language (objective-c *) with compiler, and related tools.
- Networking protocols bonjour / zeroconf
- And I probably forgot tons of stuff.
* indicates probably off-topic on SU
Every single tag I linked to in this list has questions associated with it!
This is just too damn much to be of any use. Practically as soon as it has a product page, it has a tag on this site. And the rest — well, if the combination acer&laptop isn't good enough to keep the vendor tag, then why should apple&monitor be?