It was a marriage of convenience. But like most such marriages, there comes a time when it just doesn’t work anymore.

So has been the case with Google and Apple. Despite the recent Steve Jobs-Eric Schmidt coffee date, the companies are going in two diametrically opposed directions – punctuated by Apple’s lawsuit against HTC.

Google’s primary aim is to get everyone on the web through its services to increase use of its search engine, thereby benefiting its online ad business. Hence the push for Google’s Chrome browser, Chrome OS, and Android. Apple’s cash cow comes through its proprietary hardware and software via iPad, iPhone, and iPod. If you use those devices, all official software comes exclusively through the Apple-controlled App Store.

To illustrate the point further, consider how both companies are working in the mobile space. If Google has its way by the end of the year many netbooks will be running its Chrome OS, which is essentially based on the Chrome browser. All data will live on the web, which means that developers are free to make anything they want for it as long as it’s accessible by a browser. Of course, most of your data will probably end up on Google’s servers in the form of Gmail, Docs, Calendar, etc. (I have already discussed how Google owns my soul.)

Apple, on the other hand, has created what will likely be another very popular device in the iPad. By all accounts it will have excellent apps and create a great user experience. The catch: everything goes through Cupertino. Developers from The Wall Street Journal to The White House must submit all their apps for approval.

No one vision is necessarily right, although Apple’s penchant for control raises some concerns for both users and developers. Getting data from iTunes to the iPhone is not exactly the most streamlined experience. Juggling data between an iPhone, iPad, and my PC is not a pleasant thought. Steve Jobs’s stubborn refusal to allow any Flash on the iPad has sent developers scrambling so their content is available. So instead of visiting Hulu in your browser, there will be an Apple-sanctioned app.

The web has created an expectation of liberty and openness. Let’s hope Apple’s modus operandi doesn’t change that. Not that any of  such concerns will stop the iHordes from lining up outside Apple Stores nationwide tomorrow. Of course, there is always a decent chance I will be one of them.