1. It is often preferred to base a suggestion on more than opinion or current trends when specifically referring to building a website or the technologies involved.
2. That may be true, but it is not a good reason to consider a different medium or even a "package" that optimally performs differently: Keep in mind that Google has successfully battled AT&T for the last packets of Band available in the cellular market, and the MOBI network is no longer restricted to "device programming" as it once was, as evidenced by Google and others actually giving away code to ISP's and cellular providers to compensate and to establish a more unified accessibility platform >> the very reason online capabilities in phones has increased, and the phones themselves are moving from text to "real web views" using larger screens and Windows apps.
3. Nonsense! Unsupported opinion at best. Mobi as a recognizable app is already passe, and once was the darling or "networked" businesses or even Sales-heavy enterprises/groups (i.e. Realtors, Road Warriors, Beverage Sales, etc.) as a convenient alternative to then-costly online cellular apps and limited functionality of phones vs. the ***>Bluetooth>********** evolution.
4. Prime example of a past-era MOBI platform, designed for the limited view and format of the 1st generation of cellular internet apps and fucntionality. AND, since it is not a VH Hosted website, constitutes "link seeding" which is a form of Spam (Forum Abuse), a violation of Forum Rules.
5. Again, the reason many RE groups invested early in MOBI platforms is because of the ease of implementation, as they primarily utilize the MLS DB ASPX scripting, which is particularly suited for a basic "table" format that is easily accessed online across many existing phone technologies in use.

The MOBI platform and technology is "on sale" because of the advancements in cellular online formatting, viewability, and the explosion of internet interfacing technology beoming distributed as unilaterally as an "open source" code: more phones are doing the jobs that only a short time ago could be accomplished by ***'s or the "expensive" ********** ..... now that texting is been targeted as the next "downgradable" feature of cellular, look for more Windows apps to be built in to phones, email to become elevated to the importance of a laptop (which superceeded the desktop), and more and more advertising being noticably present in the browser panes.

THAT is the bottom line, to push more of the masses online via cellular (which endangers WiFi, or hasn't anyone noticed?) because online advertising is still free and totally convertible (since the medium is already turned on to spur the purchase or the "visit").

So is MOBI worth it? Maybe....if you are dealing with the RE site you are building, and MOBI MLS "sites" are already 'standard' then maybe it is worthwhile buying a sister-domain and "mirroring" it as a DNS direct. Doing so won't force him to go out and buy a new phone, and he can still play with his peers in a cozy sandbox without "breaking tradition."
IF on the other hand, you want to prepare his site for the near-future, you may wish to consider the points I mentionjed, and Google as much as you can digest to solve today's needs without limiting the potential of tomorrow.

PS: The ".COM" extension has always been (and will always be) the Premium domain extension, and is more universally recognizable, implentable, and acceptable across all mediums and channels.
Any serious sales-oriented organization knows this, especially RE that lives and dies on multi-channel marketing efforts and networked exposure!

IMO