Only problem with this approach is ending up with multiple PNRs. This can be annoying in the case of IRROPs or changes or change fees. It also can be a problem if some but not all have status -- can't get preferred seating together, can't all get free bags, etc. And, when booking an award in coach, it can be a problem on US for those who have special dividends and can get upgraded on award tix, because splitting a PNR can prevent your companion from getting UG.

The risk for annoyance all depends on the airline and its policies. I once booked 4 award tix to OGG on HA. Pax 1 was 17,500, Pax 2 was 25,000, and Pax 3 and 4 were 30,000. I thought I was so clever booking it as 3 separate bookings to save 17,500 miles. Of course, when I ended up wanting to change and redeposit it was 3x$150 instead of $150. And when the HNL-OGG flight cancelled, HA rebooked us on different interisland flights -- wouldn't put us back together because the 17.5k was considered a different fare basis and no seats were open for the better flight for the super saver award; also super saver awards can't standby. (On the change fee issue, note that AA also gives you a break on redeposit fees for everyone on the PNR after the first.)

The whole thing was a mess. Of course, different airlines have different policies -- for those that charge redeposit or change fees per ticket not PNR (or which don't give a break for additional pax on the PNR) it doesn't matter as much, but it all can be a headache if things go sideways.