Certainly all receivers are susceptible to image frequencies and inter modulation distortion etc (including a spectrum analyzer) and susceptibility to those problems is much more likely with a wide band receiver such as the Icom R2 because of a lack of a front end filter. Also because it's a wide band receiver there tends to be more internal noise from multiple local oscillators causing even more undesired mixing. But then again it was designed to be a casual wide band receiver for listening to your local fire department, TV station or your neighbors cordless phone not to give accurate channel assessment on a tiny part of the RF spectrum. For those that use these Icoms or similar scanners for checking their 72MHz or 75 MHz channel status, adding a simple front end filter would do wonders for blocking out most of these out of band signals that can give them false readings. It could be built with bnc connectors and simply plug in between the scanner and the antenna. I can post a schematic if anyone is interested, or there are programs available for download that will calculate the component values for you when you punch in the center frequency and bandwidth you desire.
I suspect the Hobbico scanner also lacks a decent front end filter plus it is most likely a single conversion receiver making it suseptible to image frequency problems. For the price it's awesome, but seems to give some false readings particularly in dirty RF environments.
Now for the sales pitch. The RC Scan 7200 ( http://www.desert-wolfe.com/rcscan ) was specifically designed to give accurate channel assessment in the 72MHz and 75MHz band. It has a good front end filter, high quality narrow band IF filter and is a double conversion receiver. It can give you glitch counts assuming your using a standard PPM transmitter and now has a new mode of operation that allows it to scan in between channels to shows if there is interference present just outside the channel or to show if a transmitter is off frequency. This new mode isn't reflected on the website yet but will be shortly. Also, we will be standardizing on the Dual Band (72MHz & 75MHz) unit and selling it for the price of the single band units - $250.00. It also scans the band significantly faster than the Hobbico unit.
It's more expensive than the Hobbico by a fare amount, but will give you much more capability and more confidence in the readings.

Sorry, this got a little wordy.
Brian